Merge pull request #1986 from libgit2/rb/error-handling-cleanups

Clean up some error handling and change callback error behavior

109 files changed, 2325 insertions, 1637 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9c19a5a79..48cbccb4e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -33,6 +33,7 @@ OPTION( ANDROID				"Build for android NDK"	 				OFF )
 
 OPTION( USE_ICONV			"Link with and use iconv library" 		OFF )
 OPTION( USE_SSH				"Link with libssh to enable SSH support" ON )
+OPTION( VALGRIND			"Configure build for valgrind"			OFF )
 
 IF(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
 	SET( USE_ICONV ON )
@@ -340,9 +341,11 @@ IF (WIN32 AND NOT CYGWIN)
 	ADD_DEFINITIONS(-DWIN32 -D_WIN32_WINNT=0x0501)
 	FILE(GLOB SRC_OS src/win32/*.c src/win32/*.h)
 ELSEIF (AMIGA)
-	ADD_DEFINITIONS(-DNO_ADDRINFO -DNO_READDIR_R)
-	FILE(GLOB SRC_OS src/amiga/*.c src/amiga/*.h)
+	ADD_DEFINITIONS(-DNO_ADDRINFO -DNO_READDIR_R -DNO_MMAP)
 ELSE()
+	IF (VALGRIND)
+		ADD_DEFINITIONS(-DNO_MMAP)
+	ENDIF()
 	FILE(GLOB SRC_OS src/unix/*.c src/unix/*.h)
 ENDIF()
 FILE(GLOB SRC_GIT2 src/*.c src/*.h src/transports/*.c src/transports/*.h src/xdiff/*.c src/xdiff/*.h)
diff --git a/include/git2/attr.h b/include/git2/attr.h
index f256ff861..3adbb2c24 100644
--- a/include/git2/attr.h
+++ b/include/git2/attr.h
@@ -199,8 +199,9 @@ typedef int (*git_attr_foreach_cb)(const char *name, const char *value, void *pa
  *             only once per attribute name, even if there are multiple
  *             rules for a given file.  The highest priority rule will be
  *             used.  Return a non-zero value from this to stop looping.
+ *             The value will be returned from `git_attr_foreach`.
  * @param payload Passed on as extra parameter to callback function.
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_attr_foreach(
 	git_repository *repo,
diff --git a/include/git2/blob.h b/include/git2/blob.h
index dcab4fbe0..19ad4d949 100644
--- a/include/git2/blob.h
+++ b/include/git2/blob.h
@@ -159,37 +159,32 @@ typedef int (*git_blob_chunk_cb)(char *content, size_t max_length, void *payload
  * Write a loose blob to the Object Database from a
  * provider of chunks of data.
  *
- * Provided the `hintpath` parameter is filled, its value
- * will help to determine what git filters should be applied
- * to the object before it can be placed to the object database.
+ * If the `hintpath` parameter is filled, it will be used to determine
+ * what git filters should be applied to the object before it is written
+ * to the object database.
  *
+ * The implementation of the callback MUST respect the following rules:
  *
- * The implementation of the callback has to respect the
- * following rules:
+ *  - `content` must be filled by the callback. The maximum number of
+ *    bytes that the buffer can accept per call is defined by the
+ *    `max_length` parameter. Allocation and freeing of the buffer will
+ *    be taken care of by libgit2.
  *
- *  - `content` will have to be filled by the consumer. The maximum number
- * of bytes that the buffer can accept per call is defined by the
- * `max_length` parameter. Allocation and freeing of the buffer will be taken
- * care of by the function.
+ *  - The `callback` must return the number of bytes that have been
+ *    written to the `content` buffer.
  *
- *  - The callback is expected to return the number of bytes
- * that `content` have been filled with.
- *
- *  - When there is no more data to stream, the callback should
- * return 0. This will prevent it from being invoked anymore.
- *
- *  - When an error occurs, the callback should return -1.
+ *  - When there is no more data to stream, `callback` should return
+ *    0. This will prevent it from being invoked anymore.
  *
+ *  - If an error occurs, the callback should return a negative value.
+ *    This value will be returned to the caller.
  *
  * @param id Return the id of the written blob
- *
- * @param repo repository where the blob will be written.
- * This repository can be bare or not.
- *
- * @param hintpath if not NULL, will help selecting the filters
- * to apply onto the content of the blob to be created.
- *
- * @return 0 or an error code
+ * @param repo Repository where the blob will be written.
+ *        This repository can be bare or not.
+ * @param hintpath If not NULL, will be used to select data filters
+ *        to apply onto the content of the blob to be created.
+ * @return 0 or error code (from either libgit2 or callback function)
  */
 GIT_EXTERN(int) git_blob_create_fromchunks(
 	git_oid *id,
diff --git a/include/git2/checkout.h b/include/git2/checkout.h
index efafdc3e4..0e9d338c6 100644
--- a/include/git2/checkout.h
+++ b/include/git2/checkout.h
@@ -174,7 +174,12 @@ typedef enum {
  * - GIT_CHECKOUT_NOTIFY_IGNORED notifies about ignored files.
  *
  * Returning a non-zero value from this callback will cancel the checkout.
- * Notification callbacks are made prior to modifying any files on disk.
+ * The non-zero return value will be propagated back and returned by the
+ * git_checkout_... call.
+ *
+ * Notification callbacks are made prior to modifying any files on disk,
+ * so canceling on any notification will still happen prior to any files
+ * being modified.
  */
 typedef enum {
 	GIT_CHECKOUT_NOTIFY_NONE      = 0,
@@ -252,9 +257,9 @@ typedef struct git_checkout_opts {
  *
  * @param repo repository to check out (must be non-bare)
  * @param opts specifies checkout options (may be NULL)
- * @return 0 on success, GIT_EUNBORNBRANCH when HEAD points to a non existing
- * branch, GIT_ERROR otherwise (use giterr_last for information
- * about the error)
+ * @return 0 on success, GIT_EUNBORNBRANCH if HEAD points to a non
+ *         existing branch, non-zero value returned by `notify_cb`, or
+ *         other error code < 0 (use giterr_last for error details)
  */
 GIT_EXTERN(int) git_checkout_head(
 	git_repository *repo,
@@ -266,8 +271,8 @@ GIT_EXTERN(int) git_checkout_head(
  * @param repo repository into which to check out (must be non-bare)
  * @param index index to be checked out (or NULL to use repository index)
  * @param opts specifies checkout options (may be NULL)
- * @return 0 on success, GIT_ERROR otherwise (use giterr_last for information
- * about the error)
+ * @return 0 on success, non-zero return value from `notify_cb`, or error
+ *         code < 0 (use giterr_last for error details)
  */
 GIT_EXTERN(int) git_checkout_index(
 	git_repository *repo,
@@ -282,8 +287,8 @@ GIT_EXTERN(int) git_checkout_index(
  * @param treeish a commit, tag or tree which content will be used to update
  * the working directory (or NULL to use HEAD)
  * @param opts specifies checkout options (may be NULL)
- * @return 0 on success, GIT_ERROR otherwise (use giterr_last for information
- * about the error)
+ * @return 0 on success, non-zero return value from `notify_cb`, or error
+ *         code < 0 (use giterr_last for error details)
  */
 GIT_EXTERN(int) git_checkout_tree(
 	git_repository *repo,
diff --git a/include/git2/clone.h b/include/git2/clone.h
index 331cf92e7..59a73aa15 100644
--- a/include/git2/clone.h
+++ b/include/git2/clone.h
@@ -26,23 +26,25 @@ GIT_BEGIN_DECL
 /**
  * Clone options structure
  *
- * Use zeros to indicate default settings.  It's easiest to use the
- * `GIT_CLONE_OPTIONS_INIT` macro:
+ * Use the GIT_CLONE_OPTIONS_INIT to get the default settings, like this:
  *
  *		git_clone_options opts = GIT_CLONE_OPTIONS_INIT;
  *
- * - `checkout_opts` is options for the checkout step.  To disable checkout,
- *   set the `checkout_strategy` to GIT_CHECKOUT_DEFAULT.
- * - `bare` should be set to zero to create a standard repo, non-zero for
- *   a bare repo
- * - `ignore_cert_errors` should be set to 1 if errors validating the remote host's
- *   certificate should be ignored.
+ * - `checkout_opts` are option passed to the checkout step.  To disable
+ *   checkout, set the `checkout_strategy` to GIT_CHECKOUT_NONE.
+ *   Generally you will want the use GIT_CHECKOUT_SAFE_CREATE to create
+ *   all files in the working directory for the newly cloned repository.
+ * - `bare` should be set to zero (false) to create a standard repo,
+ *   or non-zero for a bare repo
+ * - `ignore_cert_errors` should be set to 1 if errors validating the
+ *   remote host's certificate should be ignored.
  *
  *   ** "origin" remote options: **
- * - `remote_name` is the name given to the "origin" remote.  The default is
- *   "origin".
- * - `checkout_branch` gives the name of the branch to checkout. NULL means
- *   use the remote's HEAD.
+ *
+ * - `remote_name` is the name to be given to the "origin" remote.  The
+ *   default is "origin".
+ * - `checkout_branch` gives the name of the branch to checkout.  NULL
+ *   means use the remote's HEAD.
  */
 
 typedef struct git_clone_options {
@@ -70,16 +72,17 @@ typedef struct git_clone_options {
  * @param out pointer that will receive the resulting repository object
  * @param url the remote repository to clone
  * @param local_path local directory to clone to
- * @param options configuration options for the clone.  If NULL, the function
- * works as though GIT_OPTIONS_INIT were passed.
- * @return 0 on success, GIT_ERROR otherwise (use giterr_last for information
- * about the error)
+ * @param options configuration options for the clone.  If NULL, the
+ *        function works as though GIT_OPTIONS_INIT were passed.
+ * @return 0 on success, any non-zero return value from a callback
+ *         function, or a negative value to indicate an error (use
+ *         `giterr_last` for a detailed error message)
  */
 GIT_EXTERN(int) git_clone(
-		git_repository **out,
-		const char *url,
-		const char *local_path,
-		const git_clone_options *options);
+	git_repository **out,
+	const char *url,
+	const char *local_path,
+	const git_clone_options *options);
 
 /**
  * Clone into a repository
@@ -91,11 +94,17 @@ GIT_EXTERN(int) git_clone(
  * @param repo the repository to use
  * @param remote the remote repository to clone from
  * @param co_opts options to use during checkout
- * @param branch the branch to checkout after the clone, pass NULL for the remote's
- * default branch
- * @return 0 on success or an error code
+ * @param branch the branch to checkout after the clone, pass NULL for the
+ *        remote's default branch
+ * @return 0 on success, any non-zero return value from a callback
+ *         function, or a negative value to indicate an error (use
+ *         `giterr_last` for a detailed error message)
  */
-GIT_EXTERN(int) git_clone_into(git_repository *repo, git_remote *remote, const git_checkout_opts *co_opts, const char *branch);
+GIT_EXTERN(int) git_clone_into(
+	git_repository *repo,
+	git_remote *remote,
+	const git_checkout_opts *co_opts,
+	const char *branch);
 
 /** @} */
 GIT_END_DECL
diff --git a/include/git2/config.h b/include/git2/config.h
index 95da4bc03..f650f1b41 100644
--- a/include/git2/config.h
+++ b/include/git2/config.h
@@ -450,13 +450,13 @@ GIT_EXTERN(int) git_config_delete_multivar(git_config *cfg, const char *name, co
  *
  * The callback receives the normalized name and value of each variable
  * in the config backend, and the data pointer passed to this function.
- * As soon as one of the callback functions returns something other than 0,
- * this function stops iterating and returns `GIT_EUSER`.
+ * If the callback returns a non-zero value, the function stops iterating
+ * and returns that value to the caller.
  *
  * @param cfg where to get the variables from
  * @param callback the function to call on each variable
  * @param payload the data to pass to the callback
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_config_foreach(
 	const git_config *cfg,
@@ -612,8 +612,8 @@ GIT_EXTERN(int) git_config_parse_int64(int64_t *out, const char *value);
 GIT_EXTERN(int) git_config_backend_foreach_match(
 	git_config_backend *backend,
 	const char *regexp,
-	int (*fn)(const git_config_entry *, void *),
-	void *data);
+	git_config_foreach_cb callback,
+	void *payload);
 
 
 /** @} */
diff --git a/include/git2/diff.h b/include/git2/diff.h
index 315cc1215..76fb23654 100644
--- a/include/git2/diff.h
+++ b/include/git2/diff.h
@@ -468,7 +468,7 @@ typedef int (*git_diff_line_cb)(
  * Flags to control the behavior of diff rename/copy detection.
  */
 typedef enum {
-	/** Obey `diff.renames`. This is overridden by any other GIT_DIFF_FIND_ALL flag. */
+	/** Obey `diff.renames`. Overridden by any other GIT_DIFF_FIND_... flag. */
 	GIT_DIFF_FIND_BY_CONFIG = 0,
 
 	/** Look for renames? (`--find-renames`) */
@@ -577,9 +577,9 @@ typedef struct {
 	unsigned int version;
 
 	/**
-	 * Combination of git_diff_find_t values (default FIND_BY_CONFIG).
-	 * Note that if you don't explicitly set this, `diff.renames` could be set
-	 * to false, resulting in `git_diff_find_similar` doing nothing. 
+	 * Combination of git_diff_find_t values (default GIT_DIFF_FIND_BY_CONFIG).
+	 * NOTE: if you don't explicitly set this, `diff.renames` could be set
+	 * to false, resulting in `git_diff_find_similar` doing nothing.
 	 */
 	uint32_t flags;
 
@@ -870,7 +870,7 @@ GIT_EXTERN(int) git_diff_is_sorted_icase(const git_diff *diff);
  * files whose only changed is a file mode change.
  *
  * Returning a non-zero value from any of the callbacks will terminate
- * the iteration and cause this return `GIT_EUSER`.
+ * the iteration and return the value to the user.
  *
  * @param diff A git_diff generated by one of the above functions.
  * @param file_cb Callback function to make per file in the diff.
@@ -881,7 +881,7 @@ GIT_EXTERN(int) git_diff_is_sorted_icase(const git_diff *diff);
  *                same callback will be made for context lines, added, and
  *                removed lines, and even for a deleted trailing newline.
  * @param payload Reference pointer that will be passed to your callbacks.
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_diff_foreach(
 	git_diff *diff,
@@ -918,13 +918,13 @@ typedef enum {
  * Iterate over a diff generating formatted text output.
  *
  * Returning a non-zero value from the callbacks will terminate the
- * iteration and cause this return `GIT_EUSER`.
+ * iteration and return the non-zero value to the caller.
  *
  * @param diff A git_diff generated by one of the above functions.
  * @param format A git_diff_format_t value to pick the text format.
  * @param print_cb Callback to make per line of diff text.
  * @param payload Reference pointer that will be passed to your callback.
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_diff_print(
 	git_diff *diff,
@@ -964,7 +964,7 @@ GIT_EXTERN(int) git_diff_print(
  * @param hunk_cb Callback for each hunk in diff; can be NULL
  * @param line_cb Callback for each line in diff; can be NULL
  * @param payload Payload passed to each callback function
- * @return 0 on success, GIT_EUSER on non-zero callback return, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_diff_blobs(
 	const git_blob *old_blob,
@@ -999,7 +999,7 @@ GIT_EXTERN(int) git_diff_blobs(
  * @param hunk_cb Callback for each hunk in diff; can be NULL
  * @param line_cb Callback for each line in diff; can be NULL
  * @param payload Payload passed to each callback function
- * @return 0 on success, GIT_EUSER on non-zero callback return, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_diff_blob_to_buffer(
 	const git_blob *old_blob,
diff --git a/include/git2/errors.h b/include/git2/errors.h
index f1a8ea1ae..973d56003 100644
--- a/include/git2/errors.h
+++ b/include/git2/errors.h
@@ -8,7 +8,6 @@
 #define INCLUDE_git_errors_h__
 
 #include "common.h"
-#include "buffer.h"
 
 /**
  * @file git2/errors.h
@@ -20,25 +19,38 @@ GIT_BEGIN_DECL
 
 /** Generic return codes */
 typedef enum {
-	GIT_OK = 0,
-	GIT_ERROR = -1,
-	GIT_ENOTFOUND = -3,
-	GIT_EEXISTS = -4,
-	GIT_EAMBIGUOUS = -5,
-	GIT_EBUFS = -6,
-	GIT_EUSER = -7,
-	GIT_EBAREREPO = -8,
-	GIT_EUNBORNBRANCH = -9,
-	GIT_EUNMERGED = -10,
-	GIT_ENONFASTFORWARD = -11,
-	GIT_EINVALIDSPEC = -12,
-	GIT_EMERGECONFLICT = -13,
-	GIT_ELOCKED = -14,
+	GIT_OK         =  0,		/*< No error */
 
-	GIT_PASSTHROUGH = -30,
-	GIT_ITEROVER = -31,
+	GIT_ERROR      = -1,		/*< Generic error */
+	GIT_ENOTFOUND  = -3,		/*< Requested object could not be found */
+	GIT_EEXISTS    = -4,		/*< Object exists preventing operation */
+	GIT_EAMBIGUOUS = -5,		/*< More than one object matches */
+	GIT_EBUFS      = -6,		/*< Output buffer too short to hold data */
+
+	/* GIT_EUSER is a special error that is never generated by libgit2
+	 * code.  You can return it from a callback (e.g to stop an iteration)
+	 * to know that it was generated by the callback and not by libgit2.
+	 */
+	GIT_EUSER      = -7,
+
+	GIT_EBAREREPO       =  -8,	/*< Operation not allowed on bare repository */
+	GIT_EUNBORNBRANCH   =  -9,	/*< HEAD refers to branch with no commits */
+	GIT_EUNMERGED       = -10,	/*< Merge in progress prevented operation */
+	GIT_ENONFASTFORWARD = -11,	/*< Reference was not fast-forwardable */
+	GIT_EINVALIDSPEC    = -12,	/*< Name/ref spec was not in a valid format */
+	GIT_EMERGECONFLICT  = -13,	/*< Merge conflicts prevented operation */
+	GIT_ELOCKED         = -14,	/*< Lock file prevented operation */
+
+	GIT_PASSTHROUGH     = -30,	/*< Internal only */
+	GIT_ITEROVER        = -31,	/*< Signals end of iteration with iterator */
 } git_error_code;
 
+/**
+ * Structure to store extra details of the last error that occurred.
+ *
+ * This is kept on a per-thread basis if GIT_THREADS was defined when the
+ * library was build, otherwise one is kept globally for the library
+ */
 typedef struct {
 	char *message;
 	int klass;
@@ -72,6 +84,7 @@ typedef enum {
 	GITERR_SSH,
 	GITERR_FILTER,
 	GITERR_REVERT,
+	GITERR_CALLBACK,
 } git_error_t;
 
 /**
@@ -91,7 +104,7 @@ GIT_EXTERN(void) giterr_clear(void);
  * Get the last error data and clear it.
  *
  * This copies the last error into the given `git_error` struct
- * and returns 0 if the copy was successful, leaving the error 
+ * and returns 0 if the copy was successful, leaving the error
  * cleared as if `giterr_clear` had been called.
  *
  * If there was no existing error in the library, -1 will be returned
diff --git a/include/git2/index.h b/include/git2/index.h
index a60db370a..ffefad15d 100644
--- a/include/git2/index.h
+++ b/include/git2/index.h
@@ -493,7 +493,7 @@ GIT_EXTERN(int) git_index_remove_bypath(git_index *index, const char *path);
  * item in the working directory immediately *before* it is added to /
  * updated in the index.  Returning zero will add the item to the index,
  * greater than zero will skip the item, and less than zero will abort the
- * scan and cause GIT_EUSER to be returned.
+ * scan and return that value to the caller.
  *
  * @param index an existing index object
  * @param pathspec array of path patterns
@@ -502,7 +502,7 @@ GIT_EXTERN(int) git_index_remove_bypath(git_index *index, const char *path);
  *                 gets index of matching pathspec entry); can be NULL;
  *                 return 0 to add, >0 to skip, <0 to abort scan.
  * @param payload payload passed through to callback function
- * @return 0 or an error code
+ * @return 0 on success, negative callback return value, or error code
  */
 GIT_EXTERN(int) git_index_add_all(
 	git_index *index,
@@ -524,7 +524,7 @@ GIT_EXTERN(int) git_index_add_all(
  *                 gets index of matching pathspec entry); can be NULL;
  *                 return 0 to add, >0 to skip, <0 to abort scan.
  * @param payload payload passed through to callback function
- * @return 0 or an error code
+ * @return 0 on success, negative callback return value, or error code
  */
 GIT_EXTERN(int) git_index_remove_all(
 	git_index *index,
@@ -553,7 +553,7 @@ GIT_EXTERN(int) git_index_remove_all(
  *                 gets index of matching pathspec entry); can be NULL;
  *                 return 0 to add, >0 to skip, <0 to abort scan.
  * @param payload payload passed through to callback function
- * @return 0 or an error code
+ * @return 0 on success, negative callback return value, or error code
  */
 GIT_EXTERN(int) git_index_update_all(
 	git_index *index,
diff --git a/include/git2/notes.h b/include/git2/notes.h
index 76361633b..0cb6ce5f1 100644
--- a/include/git2/notes.h
+++ b/include/git2/notes.h
@@ -189,7 +189,7 @@ GIT_EXTERN(int) git_note_default_ref(const char **out, git_repository *repo);
  *
  * @param payload Extra parameter to callback function.
  *
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_note_foreach(
 	git_repository *repo,
diff --git a/include/git2/odb.h b/include/git2/odb.h
index ad56384f0..82df4d300 100644
--- a/include/git2/odb.h
+++ b/include/git2/odb.h
@@ -189,7 +189,7 @@ GIT_EXTERN(int) git_odb_refresh(struct git_odb *db);
  * @param db database to use
  * @param cb the callback to call for each object
  * @param payload data to pass to the callback
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_odb_foreach(git_odb *db, git_odb_foreach_cb cb, void *payload);
 
diff --git a/include/git2/pack.h b/include/git2/pack.h
index 88a2716bb..11bb559d8 100644
--- a/include/git2/pack.h
+++ b/include/git2/pack.h
@@ -52,7 +52,7 @@ typedef enum {
 	GIT_PACKBUILDER_ADDING_OBJECTS = 0,
 	GIT_PACKBUILDER_DELTAFICATION = 1,
 } git_packbuilder_stage_t;
-	
+
 /**
  * Initialize a new packbuilder
  *
@@ -143,6 +143,7 @@ GIT_EXTERN(int) git_packbuilder_write(
 GIT_EXTERN(const git_oid *) git_packbuilder_hash(git_packbuilder *pb);
 
 typedef int (*git_packbuilder_foreach_cb)(void *buf, size_t size, void *payload);
+
 /**
  * Create the new pack and pass each object to the callback
  *
diff --git a/include/git2/patch.h b/include/git2/patch.h
index 6a6ad92d7..e09f625c0 100644
--- a/include/git2/patch.h
+++ b/include/git2/patch.h
@@ -218,13 +218,13 @@ GIT_EXTERN(size_t) git_patch_size(
  * Serialize the patch to text via callback.
  *
  * Returning a non-zero value from the callback will terminate the iteration
- * and cause this return `GIT_EUSER`.
+ * and return that value to the caller.
  *
  * @param patch A git_patch representing changes to one file
  * @param print_cb Callback function to output lines of the patch.  Will be
  *                 called for file headers, hunk headers, and diff lines.
  * @param payload Reference pointer that will be passed to your callbacks.
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_patch_print(
 	git_patch *patch,
diff --git a/include/git2/push.h b/include/git2/push.h
index 77ef74039..12f0e7f2c 100644
--- a/include/git2/push.h
+++ b/include/git2/push.h
@@ -132,17 +132,19 @@ GIT_EXTERN(int) git_push_finish(git_push *push);
 GIT_EXTERN(int) git_push_unpack_ok(git_push *push);
 
 /**
- * Call callback `cb' on each status
+ * Invoke callback `cb' on each status entry
  *
  * For each of the updated references, we receive a status report in the
  * form of `ok refs/heads/master` or `ng refs/heads/master <msg>`.
  * `msg != NULL` means the reference has not been updated for the given
  * reason.
  *
+ * Return a non-zero value from the callback to stop the loop.
+ *
  * @param push The push object
  * @param cb The callback to call on each object
  *
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_push_status_foreach(git_push *push,
 			int (*cb)(const char *ref, const char *msg, void *data),
diff --git a/include/git2/refs.h b/include/git2/refs.h
index 4041947f6..e2bfa9615 100644
--- a/include/git2/refs.h
+++ b/include/git2/refs.h
@@ -310,20 +310,33 @@ typedef int (*git_reference_foreach_name_cb)(const char *name, void *payload);
  * Perform a callback on each reference in the repository.
  *
  * The `callback` function will be called for each reference in the
- * repository, receiving the name of the reference and the `payload` value
+ * repository, receiving the reference object and the `payload` value
  * passed to this method.  Returning a non-zero value from the callback
  * will terminate the iteration.
  *
  * @param repo Repository where to find the refs
  * @param callback Function which will be called for every listed ref
  * @param payload Additional data to pass to the callback
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_reference_foreach(
 	git_repository *repo,
 	git_reference_foreach_cb callback,
 	void *payload);
 
+/**
+ * Perform a callback on the fully-qualified name of each reference.
+ *
+ * The `callback` function will be called for each reference in the
+ * repository, receiving the name of the reference and the `payload` value
+ * passed to this method.  Returning a non-zero value from the callback
+ * will terminate the iteration.
+ *
+ * @param repo Repository where to find the refs
+ * @param callback Function which will be called for every listed ref name
+ * @param payload Additional data to pass to the callback
+ * @return 0 on success, non-zero callback return value, or error code
+ */
 GIT_EXTERN(int) git_reference_foreach_name(
 	git_repository *repo,
 	git_reference_foreach_name_cb callback,
diff --git a/include/git2/repository.h b/include/git2/repository.h
index c6bd4dca4..9f71d2959 100644
--- a/include/git2/repository.h
+++ b/include/git2/repository.h
@@ -503,14 +503,18 @@ typedef int (*git_repository_fetchhead_foreach_cb)(const char *ref_name,
 	void *payload);
 
 /**
- * Call callback 'callback' for each entry in the given FETCH_HEAD file.
+ * Invoke 'callback' for each entry in the given FETCH_HEAD file.
+ *
+ * Return a non-zero value from the callback to stop the loop.
  *
  * @param repo A repository object
  * @param callback Callback function
  * @param payload Pointer to callback data (optional)
- * @return 0 on success, GIT_ENOTFOUND, GIT_EUSER or error
+ * @return 0 on success, non-zero callback return value, GIT_ENOTFOUND if
+ *         there is no FETCH_HEAD file, or other error code.
  */
-GIT_EXTERN(int) git_repository_fetchhead_foreach(git_repository *repo,
+GIT_EXTERN(int) git_repository_fetchhead_foreach(
+	git_repository *repo,
 	git_repository_fetchhead_foreach_cb callback,
 	void *payload);
 
@@ -518,15 +522,19 @@ typedef int (*git_repository_mergehead_foreach_cb)(const git_oid *oid,
 	void *payload);
 
 /**
- * If a merge is in progress, call callback 'cb' for each commit ID in the
+ * If a merge is in progress, invoke 'callback' for each commit ID in the
  * MERGE_HEAD file.
  *
+ * Return a non-zero value from the callback to stop the loop.
+ *
  * @param repo A repository object
  * @param callback Callback function
  * @param payload Pointer to callback data (optional)
- * @return 0 on success, GIT_ENOTFOUND, GIT_EUSER or error
+ * @return 0 on success, non-zero callback return value, GIT_ENOTFOUND if
+ *         there is no MERGE_HEAD file, or other error code.
  */
-GIT_EXTERN(int) git_repository_mergehead_foreach(git_repository *repo,
+GIT_EXTERN(int) git_repository_mergehead_foreach(
+	git_repository *repo,
 	git_repository_mergehead_foreach_cb callback,
 	void *payload);
 
diff --git a/include/git2/stash.h b/include/git2/stash.h
index b48d33f5d..e2fe2cf0b 100644
--- a/include/git2/stash.h
+++ b/include/git2/stash.h
@@ -62,19 +62,15 @@ GIT_EXTERN(int) git_stash_save(
 	unsigned int flags);
 
 /**
- * When iterating over all the stashed states, callback that will be
- * issued per entry.
+ * This is a callback function you can provide to iterate over all the
+ * stashed states that will be invoked per entry.
  *
  * @param index The position within the stash list. 0 points to the
- * most recent stashed state.
- *
+ *              most recent stashed state.
  * @param message The stash message.
- *
  * @param stash_id The commit oid of the stashed state.
- *
  * @param payload Extra parameter to callback function.
- *
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 to continue iterating or non-zero to stop
  */
 typedef int (*git_stash_cb)(
 	size_t index,
@@ -89,12 +85,12 @@ typedef int (*git_stash_cb)(
  *
  * @param repo Repository where to find the stash.
  *
- * @param callback Callback to invoke per found stashed state. The most recent
- * stash state will be enumerated first.
+ * @param callback Callback to invoke per found stashed state. The most
+ *                 recent stash state will be enumerated first.
  *
  * @param payload Extra parameter to callback function.
  *
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_stash_foreach(
 	git_repository *repo,
diff --git a/include/git2/status.h b/include/git2/status.h
index 4ec3432df..aa68c0da0 100644
--- a/include/git2/status.h
+++ b/include/git2/status.h
@@ -203,12 +203,12 @@ typedef struct {
  * into this function.
  *
  * If the callback returns a non-zero value, this function will stop looping
- * and return GIT_EUSER.
+ * and return that value to caller.
  *
  * @param repo A repository object
  * @param callback The function to call on each file
  * @param payload Pointer to pass through to callback function
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_status_foreach(
 	git_repository *repo,
@@ -227,7 +227,7 @@ GIT_EXTERN(int) git_status_foreach(
  * @param opts Status options structure
  * @param callback The function to call on each file
  * @param payload Pointer to pass through to callback function
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_status_foreach_ext(
 	git_repository *repo,
diff --git a/include/git2/sys/filter.h b/include/git2/sys/filter.h
index 94ad3aed4..8fe21c9c0 100644
--- a/include/git2/sys/filter.h
+++ b/include/git2/sys/filter.h
@@ -149,6 +149,7 @@ typedef int (*git_filter_init_fn)(git_filter *self);
  * Specified as `filter.shutdown`, this is an optional callback invoked
  * when the filter is unregistered or when libgit2 is shutting down.  It
  * will be called once at most and should release resources as needed.
+ * This may be called even if the `initialize` callback was not made.
  *
  * Typically this function will free the `git_filter` object itself.
  */
diff --git a/include/git2/tree.h b/include/git2/tree.h
index d94b446c2..422365674 100644
--- a/include/git2/tree.h
+++ b/include/git2/tree.h
@@ -332,11 +332,18 @@ GIT_EXTERN(int) git_treebuilder_insert(
 GIT_EXTERN(int) git_treebuilder_remove(
 	git_treebuilder *bld, const char *filename);
 
+/**
+ * Callback for git_treebuilder_filter
+ *
+ * The return value is treated as a boolean, with zero indicating that the
+ * entry should be left alone and any non-zero value meaning that the
+ * entry should be removed from the treebuilder list (i.e. filtered out).
+ */
 typedef int (*git_treebuilder_filter_cb)(
 	const git_tree_entry *entry, void *payload);
 
 /**
- * Filter the entries in the tree
+ * Selectively remove entries in the tree
  *
  * The `filter` callback will be called for each entry in the tree with a
  * pointer to the entry and the provided `payload`; if the callback returns
@@ -344,7 +351,7 @@ typedef int (*git_treebuilder_filter_cb)(
  *
  * @param bld Tree builder
  * @param filter Callback to filter entries
- * @param payload Extra data to pass to filter
+ * @param payload Extra data to pass to filter callback
  */
 GIT_EXTERN(void) git_treebuilder_filter(
 	git_treebuilder *bld,
diff --git a/src/amiga/map.c b/src/amiga/map.c
deleted file mode 100644
index 0ba7995c6..000000000
--- a/src/amiga/map.c
+++ /dev/null
@@ -1,48 +0,0 @@
-/*
- * Copyright (C) the libgit2 contributors. All rights reserved.
- *
- * This file is part of libgit2, distributed under the GNU GPL v2 with
- * a Linking Exception. For full terms see the included COPYING file.
- */
-#include <git2/common.h>
-
-#ifndef GIT_WIN32
-
-#include "posix.h"
-#include "map.h"
-#include <errno.h>
-
-int p_mmap(git_map *out, size_t len, int prot, int flags, int fd, git_off_t offset)
-{
-	GIT_MMAP_VALIDATE(out, len, prot, flags);
-
-	out->data = NULL;
-	out->len = 0;
-
-	if ((prot & GIT_PROT_WRITE) && ((flags & GIT_MAP_TYPE) == GIT_MAP_SHARED)) {
-		giterr_set(GITERR_OS, "Trying to map shared-writeable");
-		return -1;
-	}
-
-	out->data = malloc(len);
-	GITERR_CHECK_ALLOC(out->data);
-
-	if ((p_lseek(fd, offset, SEEK_SET) < 0) || ((size_t)p_read(fd, out->data, len) != len)) {
-		giterr_set(GITERR_OS, "mmap emulation failed");
-		return -1;
-	}
-
-	out->len = len;
-	return 0;
-}
-
-int p_munmap(git_map *map)
-{
-	assert(map != NULL);
-	free(map->data);
-
-	return 0;
-}
-
-#endif
-
diff --git a/src/attr.c b/src/attr.c
index 98a328a55..e6e274e42 100644
--- a/src/attr.c
+++ b/src/attr.c
@@ -193,8 +193,7 @@ int git_attr_foreach(
 
 				error = callback(assign->name, assign->value, payload);
 				if (error) {
-					giterr_clear();
-					error = GIT_EUSER;
+					giterr_set_after_callback(error);
 					goto cleanup;
 				}
 			}
@@ -536,7 +535,7 @@ static int collect_attr_files(
 	int error;
 	git_buf dir = GIT_BUF_INIT;
 	const char *workdir = git_repository_workdir(repo);
-	attr_walk_up_info info;
+	attr_walk_up_info info = { NULL };
 
 	if (git_attr_cache__init(repo) < 0 ||
 		git_vector_init(files, 4, NULL) < 0)
@@ -603,11 +602,15 @@ static int attr_cache__lookup_path(
 {
 	git_buf buf = GIT_BUF_INIT;
 	int error;
-	const char *cfgval = NULL;
+	const git_config_entry *entry = NULL;
 
 	*out = NULL;
 
-	if (!(error = git_config_get_string(&cfgval, cfg, key))) {
+	if ((error = git_config__lookup_entry(&entry, cfg, key, false)) < 0)
+		return error;
+
+	if (entry) {
+		const char *cfgval = entry->value;
 
 		/* expand leading ~/ as needed */
 		if (cfgval && cfgval[0] == '~' && cfgval[1] == '/' &&
@@ -616,13 +619,9 @@ static int attr_cache__lookup_path(
 		else if (cfgval)
 			*out = git__strdup(cfgval);
 
-	} else if (error == GIT_ENOTFOUND) {
-		giterr_clear();
-		error = 0;
-
-		if (!git_futils_find_xdg_file(&buf, fallback))
-			*out = git_buf_detach(&buf);
 	}
+	else if (!git_futils_find_xdg_file(&buf, fallback))
+		*out = git_buf_detach(&buf);
 
 	git_buf_free(&buf);
 
diff --git a/src/blame.c b/src/blame.c
index ea9f77af5..a1357415a 100644
--- a/src/blame.c
+++ b/src/blame.c
@@ -108,17 +108,23 @@ git_blame* git_blame__alloc(
 	git_blame_options opts,
 	const char *path)
 {
-	git_blame *gbr = (git_blame*)git__calloc(1, sizeof(git_blame));
-	if (!gbr) {
-		giterr_set_oom();
+	git_blame *gbr = git__calloc(1, sizeof(git_blame));
+	if (!gbr)
 		return NULL;
-	}
-	git_vector_init(&gbr->hunks, 8, hunk_cmp);
-	git_vector_init(&gbr->paths, 8, paths_cmp);
+
 	gbr->repository = repo;
 	gbr->options = opts;
-	gbr->path = git__strdup(path);
-	git_vector_insert(&gbr->paths, git__strdup(path));
+
+	if (git_vector_init(&gbr->hunks, 8, hunk_cmp) < 0 ||
+		git_vector_init(&gbr->paths, 8, paths_cmp) < 0 ||
+		(gbr->path = git__strdup(path)) == NULL ||
+		git_vector_insert(&gbr->paths, git__strdup(path)) < 0)
+	{
+		git_blame_free(gbr);
+		git__free(gbr);
+		return NULL;
+	}
+
 	return gbr;
 }
 
@@ -126,7 +132,6 @@ void git_blame_free(git_blame *blame)
 {
 	size_t i;
 	git_blame_hunk *hunk;
-	char *path;
 
 	if (!blame) return;
 
@@ -134,13 +139,11 @@ void git_blame_free(git_blame *blame)
 		free_hunk(hunk);
 	git_vector_free(&blame->hunks);
 
-	git_vector_foreach(&blame->paths, i, path)
-		git__free(path);
-	git_vector_free(&blame->paths);
+	git_vector_free_deep(&blame->paths);
 
 	git_array_clear(blame->line_index);
 
-	git__free((void*)blame->path);
+	git__free(blame->path);
 	git_blob_free(blame->final_blob);
 	git__free(blame);
 }
diff --git a/src/blame.h b/src/blame.h
index 637e43985..7e23de808 100644
--- a/src/blame.h
+++ b/src/blame.h
@@ -64,7 +64,7 @@ typedef struct git_blame__entry {
 } git_blame__entry;
 
 struct git_blame {
-	const char *path;
+	char *path;
 	git_repository *repository;
 	git_blame_options options;
 
diff --git a/src/blob.c b/src/blob.c
index 2c6d52800..ab344ae98 100644
--- a/src/blob.c
+++ b/src/blob.c
@@ -272,37 +272,44 @@ int git_blob_create_fromchunks(
 	int (*source_cb)(char *content, size_t max_length, void *payload),
 	void *payload)
 {
-	int error = -1, read_bytes;
+	int error;
 	char *content = NULL;
 	git_filebuf file = GIT_FILEBUF_INIT;
 	git_buf path = GIT_BUF_INIT;
 
-	if (git_buf_joinpath(
-			&path, git_repository_path(repo), GIT_OBJECTS_DIR "streamed") < 0)
+	assert(oid && repo && source_cb);
+
+	if ((error = git_buf_joinpath(
+			&path, git_repository_path(repo), GIT_OBJECTS_DIR "streamed")) < 0)
 		goto cleanup;
 
 	content = git__malloc(BUFFER_SIZE);
 	GITERR_CHECK_ALLOC(content);
 
-	if (git_filebuf_open(&file, git_buf_cstr(&path), GIT_FILEBUF_TEMPORARY, 0666) < 0)
+	if ((error = git_filebuf_open(
+			&file, git_buf_cstr(&path), GIT_FILEBUF_TEMPORARY, 0666)) < 0)
 		goto cleanup;
 
 	while (1) {
-		read_bytes = source_cb(content, BUFFER_SIZE, payload);
-
-		assert(read_bytes <= BUFFER_SIZE);
+		int read_bytes = source_cb(content, BUFFER_SIZE, payload);
 
-		if (read_bytes <= 0)
+		if (!read_bytes)
 			break;
 
-		if (git_filebuf_write(&file, content, read_bytes) < 0)
+		if (read_bytes > BUFFER_SIZE) {
+			giterr_set(GITERR_OBJECT, "Invalid chunk size while creating blob");
+			error = GIT_EBUFS;
+		} else if (read_bytes < 0) {
+			error = giterr_set_after_callback(read_bytes);
+		} else {
+			error = git_filebuf_write(&file, content, read_bytes);
+		}
+
+		if (error < 0)
 			goto cleanup;
 	}
 
-	if (read_bytes < 0)
-		goto cleanup;
-
-	if (git_filebuf_flush(&file) < 0)
+	if ((error = git_filebuf_flush(&file)) < 0)
 		goto cleanup;
 
 	error = git_blob__create_from_paths(
@@ -312,6 +319,7 @@ cleanup:
 	git_buf_free(&path);
 	git_filebuf_cleanup(&file);
 	git__free(content);
+
 	return error;
 }
 
diff --git a/src/branch.c b/src/branch.c
index 95b3fd980..ef71c2cd1 100644
--- a/src/branch.c
+++ b/src/branch.c
@@ -90,29 +90,28 @@ int git_branch_delete(git_reference *branch)
 
 	assert(branch);
 
-	if (!git_reference_is_branch(branch) &&
-		!git_reference_is_remote(branch)) {
-		giterr_set(GITERR_INVALID, "Reference '%s' is not a valid branch.", git_reference_name(branch));
-		return -1;
+	if (!git_reference_is_branch(branch) && !git_reference_is_remote(branch)) {
+		giterr_set(GITERR_INVALID, "Reference '%s' is not a valid branch.",
+			git_reference_name(branch));
+		return GIT_ENOTFOUND;
 	}
 
 	if ((is_head = git_branch_is_head(branch)) < 0)
 		return is_head;
 
 	if (is_head) {
-		giterr_set(GITERR_REFERENCE,
-				"Cannot delete branch '%s' as it is the current HEAD of the repository.", git_reference_name(branch));
+		giterr_set(GITERR_REFERENCE, "Cannot delete branch '%s' as it is "
+			"the current HEAD of the repository.", git_reference_name(branch));
 		return -1;
 	}
 
-	if (git_buf_printf(&config_section, "branch.%s", git_reference_name(branch) + strlen(GIT_REFS_HEADS_DIR)) < 0)
+	if (git_buf_join(&config_section, '.', "branch",
+			git_reference_name(branch) + strlen(GIT_REFS_HEADS_DIR)) < 0)
 		goto on_error;
 
 	if (git_config_rename_section(
-		git_reference_owner(branch), 
-		git_buf_cstr(&config_section),
-		NULL) < 0)
-			goto on_error;
+		git_reference_owner(branch), git_buf_cstr(&config_section), NULL) < 0)
+		goto on_error;
 
 	if (git_reference_delete(branch) < 0)
 		goto on_error;
@@ -206,17 +205,21 @@ int git_branch_move(
 	if (error < 0)
 		goto done;
 
-	git_buf_printf(&old_config_section,
-		"branch.%s", git_reference_name(branch) + strlen(GIT_REFS_HEADS_DIR));
-
-	git_buf_printf(&new_config_section, "branch.%s", new_branch_name);
+	/* first update ref then config so failure won't trash config */
 
-	if ((error = git_config_rename_section(git_reference_owner(branch),
-		git_buf_cstr(&old_config_section),
-		git_buf_cstr(&new_config_section))) < 0)
+	error = git_reference_rename(
+		out, branch, git_buf_cstr(&new_reference_name), force);
+	if (error < 0)
 		goto done;
 
-	error = git_reference_rename(out, branch, git_buf_cstr(&new_reference_name), force);
+	git_buf_join(&old_config_section, '.', "branch",
+		git_reference_name(branch) + strlen(GIT_REFS_HEADS_DIR));
+	git_buf_join(&new_config_section, '.', "branch", new_branch_name);
+
+	error = git_config_rename_section(
+		git_reference_owner(branch),
+		git_buf_cstr(&old_config_section),
+		git_buf_cstr(&new_config_section));
 
 done:
 	git_buf_free(&new_reference_name);
diff --git a/src/checkout.c b/src/checkout.c
index 6d7e3cfd4..0f30d16f3 100644
--- a/src/checkout.c
+++ b/src/checkout.c
@@ -83,10 +83,8 @@ static int checkout_notify(
 	const git_diff_file *baseline = NULL, *target = NULL, *workdir = NULL;
 	const char *path = NULL;
 
-	if (!data->opts.notify_cb)
-		return 0;
-
-	if ((why & data->opts.notify_flags) == 0)
+	if (!data->opts.notify_cb ||
+		(why & data->opts.notify_flags) == 0)
 		return 0;
 
 	if (wditem) {
@@ -125,8 +123,13 @@ static int checkout_notify(
 		path = delta->old_file.path;
 	}
 
-	return data->opts.notify_cb(
-		why, path, baseline, target, workdir, data->opts.notify_payload);
+	{
+		int error = data->opts.notify_cb(
+			why, path, baseline, target, workdir, data->opts.notify_payload);
+
+		return giterr_set_after_callback_function(
+			error, "git_checkout notification");
+	}
 }
 
 static bool checkout_is_workdir_modified(
@@ -186,69 +189,66 @@ static bool checkout_is_workdir_modified(
 	((data->strategy & GIT_CHECKOUT_##FLAG) ? CHECKOUT_ACTION__##YES : CHECKOUT_ACTION__##NO)
 
 static int checkout_action_common(
+	int *action,
 	checkout_data *data,
-	int action,
 	const git_diff_delta *delta,
 	const git_index_entry *wd)
 {
 	git_checkout_notify_t notify = GIT_CHECKOUT_NOTIFY_NONE;
 
-	if (action <= 0)
-		return action;
-
 	if ((data->strategy & GIT_CHECKOUT_UPDATE_ONLY) != 0)
-		action = (action & ~CHECKOUT_ACTION__REMOVE);
+		*action = (*action & ~CHECKOUT_ACTION__REMOVE);
 
-	if ((action & CHECKOUT_ACTION__UPDATE_BLOB) != 0) {
+	if ((*action & CHECKOUT_ACTION__UPDATE_BLOB) != 0) {
 		if (S_ISGITLINK(delta->new_file.mode))
-			action = (action & ~CHECKOUT_ACTION__UPDATE_BLOB) |
+			*action = (*action & ~CHECKOUT_ACTION__UPDATE_BLOB) |
 				CHECKOUT_ACTION__UPDATE_SUBMODULE;
 
 		/* to "update" a symlink, we must remove the old one first */
 		if (delta->new_file.mode == GIT_FILEMODE_LINK && wd != NULL)
-			action |= CHECKOUT_ACTION__REMOVE;
+			*action |= CHECKOUT_ACTION__REMOVE;
 
 		notify = GIT_CHECKOUT_NOTIFY_UPDATED;
 	}
 
-	if ((action & CHECKOUT_ACTION__CONFLICT) != 0)
+	if ((*action & CHECKOUT_ACTION__CONFLICT) != 0)
 		notify = GIT_CHECKOUT_NOTIFY_CONFLICT;
 
-	if (notify != GIT_CHECKOUT_NOTIFY_NONE &&
-		checkout_notify(data, notify, delta, wd) != 0)
-		return GIT_EUSER;
-
-	return action;
+	return checkout_notify(data, notify, delta, wd);
 }
 
 static int checkout_action_no_wd(
+	int *action,
 	checkout_data *data,
 	const git_diff_delta *delta)
 {
-	int action = CHECKOUT_ACTION__NONE;
+	int error = 0;
+
+	*action = CHECKOUT_ACTION__NONE;
 
 	switch (delta->status) {
 	case GIT_DELTA_UNMODIFIED: /* case 12 */
-		if (checkout_notify(data, GIT_CHECKOUT_NOTIFY_DIRTY, delta, NULL))
-			return GIT_EUSER;
-		action = CHECKOUT_ACTION_IF(SAFE_CREATE, UPDATE_BLOB, NONE);
+		error = checkout_notify(data, GIT_CHECKOUT_NOTIFY_DIRTY, delta, NULL);
+		if (error)
+			return error;
+		*action = CHECKOUT_ACTION_IF(SAFE_CREATE, UPDATE_BLOB, NONE);
 		break;
 	case GIT_DELTA_ADDED:    /* case 2 or 28 (and 5 but not really) */
-		action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
+		*action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
 		break;
 	case GIT_DELTA_MODIFIED: /* case 13 (and 35 but not really) */
-		action = CHECKOUT_ACTION_IF(SAFE_CREATE, UPDATE_BLOB, CONFLICT);
+		*action = CHECKOUT_ACTION_IF(SAFE_CREATE, UPDATE_BLOB, CONFLICT);
 		break;
 	case GIT_DELTA_TYPECHANGE: /* case 21 (B->T) and 28 (T->B)*/
 		if (delta->new_file.mode == GIT_FILEMODE_TREE)
-			action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
+			*action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
 		break;
 	case GIT_DELTA_DELETED: /* case 8 or 25 */
 	default: /* impossible */
 		break;
 	}
 
-	return checkout_action_common(data, action, delta, NULL);
+	return checkout_action_common(action, data, delta, NULL);
 }
 
 static int checkout_action_wd_only(
@@ -257,6 +257,7 @@ static int checkout_action_wd_only(
 	const git_index_entry *wd,
 	git_vector *pathspec)
 {
+	int error = 0;
 	bool remove = false;
 	git_checkout_notify_t notify = GIT_CHECKOUT_NOTIFY_NONE;
 
@@ -269,13 +270,13 @@ static int checkout_action_wd_only(
 	/* check if item is tracked in the index but not in the checkout diff */
 	if (data->index != NULL) {
 		if (wd->mode != GIT_FILEMODE_TREE) {
-			int error;
-
-			if ((error = git_index_find(NULL, data->index, wd->path)) == 0) {
+			if (!(error = git_index_find(NULL, data->index, wd->path))) {
 				notify = GIT_CHECKOUT_NOTIFY_DIRTY;
 				remove = ((data->strategy & GIT_CHECKOUT_FORCE) != 0);
 			} else if (error != GIT_ENOTFOUND)
 				return error;
+			else
+				giterr_clear();
 		} else {
 			/* for tree entries, we have to see if there are any index
 			 * entries that are contained inside that tree
@@ -301,18 +302,16 @@ static int checkout_action_wd_only(
 		remove = ((data->strategy & GIT_CHECKOUT_REMOVE_UNTRACKED) != 0);
 	}
 
-	if (checkout_notify(data, notify, NULL, wd))
-		return GIT_EUSER;
+	error = checkout_notify(data, notify, NULL, wd);
 
-	if (remove) {
+	if (!error && remove) {
 		char *path = git_pool_strdup(&data->pool, wd->path);
 		GITERR_CHECK_ALLOC(path);
 
-		if (git_vector_insert(&data->removes, path) < 0)
-			return -1;
+		error = git_vector_insert(&data->removes, path);
 	}
 
-	return 0;
+	return error;
 }
 
 static bool submodule_is_config_only(
@@ -331,35 +330,35 @@ static bool submodule_is_config_only(
 }
 
 static int checkout_action_with_wd(
+	int *action,
 	checkout_data *data,
 	const git_diff_delta *delta,
 	const git_index_entry *wd)
 {
-	int action = CHECKOUT_ACTION__NONE;
+	*action = CHECKOUT_ACTION__NONE;
 
 	switch (delta->status) {
 	case GIT_DELTA_UNMODIFIED: /* case 14/15 or 33 */
 		if (checkout_is_workdir_modified(data, &delta->old_file, wd)) {
-			if (checkout_notify(
-					data, GIT_CHECKOUT_NOTIFY_DIRTY, delta, wd))
-				return GIT_EUSER;
-			action = CHECKOUT_ACTION_IF(FORCE, UPDATE_BLOB, NONE);
+			GITERR_CHECK_ERROR(
+				checkout_notify(data, GIT_CHECKOUT_NOTIFY_DIRTY, delta, wd) );
+			*action = CHECKOUT_ACTION_IF(FORCE, UPDATE_BLOB, NONE);
 		}
 		break;
 	case GIT_DELTA_ADDED: /* case 3, 4 or 6 */
-		action = CHECKOUT_ACTION_IF(FORCE, UPDATE_BLOB, CONFLICT);
+		*action = CHECKOUT_ACTION_IF(FORCE, UPDATE_BLOB, CONFLICT);
 		break;
 	case GIT_DELTA_DELETED: /* case 9 or 10 (or 26 but not really) */
 		if (checkout_is_workdir_modified(data, &delta->old_file, wd))
-			action = CHECKOUT_ACTION_IF(FORCE, REMOVE, CONFLICT);
+			*action = CHECKOUT_ACTION_IF(FORCE, REMOVE, CONFLICT);
 		else
-			action = CHECKOUT_ACTION_IF(SAFE, REMOVE, NONE);
+			*action = CHECKOUT_ACTION_IF(SAFE, REMOVE, NONE);
 		break;
 	case GIT_DELTA_MODIFIED: /* case 16, 17, 18 (or 36 but not really) */
 		if (checkout_is_workdir_modified(data, &delta->old_file, wd))
-			action = CHECKOUT_ACTION_IF(FORCE, UPDATE_BLOB, CONFLICT);
+			*action = CHECKOUT_ACTION_IF(FORCE, UPDATE_BLOB, CONFLICT);
 		else
-			action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
+			*action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
 		break;
 	case GIT_DELTA_TYPECHANGE: /* case 22, 23, 29, 30 */
 		if (delta->old_file.mode == GIT_FILEMODE_TREE) {
@@ -367,92 +366,93 @@ static int checkout_action_with_wd(
 				/* either deleting items in old tree will delete the wd dir,
 				 * or we'll get a conflict when we attempt blob update...
 				 */
-				action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
+				*action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
 			else if (wd->mode == GIT_FILEMODE_COMMIT) {
 				/* workdir is possibly a "phantom" submodule - treat as a
 				 * tree if the only submodule info came from the config
 				 */
 				if (submodule_is_config_only(data, wd->path))
-					action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
+					*action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
 				else
-					action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
+					*action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
 			} else
-				action = CHECKOUT_ACTION_IF(FORCE, REMOVE, CONFLICT);
+				*action = CHECKOUT_ACTION_IF(FORCE, REMOVE, CONFLICT);
 		}
 		else if (checkout_is_workdir_modified(data, &delta->old_file, wd))
-			action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
+			*action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
 		else
-			action = CHECKOUT_ACTION_IF(SAFE, REMOVE_AND_UPDATE, NONE);
+			*action = CHECKOUT_ACTION_IF(SAFE, REMOVE_AND_UPDATE, NONE);
 
 		/* don't update if the typechange is to a tree */
 		if (delta->new_file.mode == GIT_FILEMODE_TREE)
-			action = (action & ~CHECKOUT_ACTION__UPDATE_BLOB);
+			*action = (*action & ~CHECKOUT_ACTION__UPDATE_BLOB);
 		break;
 	default: /* impossible */
 		break;
 	}
 
-	return checkout_action_common(data, action, delta, wd);
+	return checkout_action_common(action, data, delta, wd);
 }
 
 static int checkout_action_with_wd_blocker(
+	int *action,
 	checkout_data *data,
 	const git_diff_delta *delta,
 	const git_index_entry *wd)
 {
-	int action = CHECKOUT_ACTION__NONE;
+	*action = CHECKOUT_ACTION__NONE;
 
 	switch (delta->status) {
 	case GIT_DELTA_UNMODIFIED:
 		/* should show delta as dirty / deleted */
-		if (checkout_notify(data, GIT_CHECKOUT_NOTIFY_DIRTY, delta, wd))
-			return GIT_EUSER;
-		action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, NONE);
+		GITERR_CHECK_ERROR(
+			checkout_notify(data, GIT_CHECKOUT_NOTIFY_DIRTY, delta, wd) );
+		*action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, NONE);
 		break;
 	case GIT_DELTA_ADDED:
 	case GIT_DELTA_MODIFIED:
-		action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
+		*action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
 		break;
 	case GIT_DELTA_DELETED:
-		action = CHECKOUT_ACTION_IF(FORCE, REMOVE, CONFLICT);
+		*action = CHECKOUT_ACTION_IF(FORCE, REMOVE, CONFLICT);
 		break;
 	case GIT_DELTA_TYPECHANGE:
 		/* not 100% certain about this... */
-		action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
+		*action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
 		break;
 	default: /* impossible */
 		break;
 	}
 
-	return checkout_action_common(data, action, delta, wd);
+	return checkout_action_common(action, data, delta, wd);
 }
 
 static int checkout_action_with_wd_dir(
+	int *action,
 	checkout_data *data,
 	const git_diff_delta *delta,
 	const git_index_entry *wd)
 {
-	int action = CHECKOUT_ACTION__NONE;
+	*action = CHECKOUT_ACTION__NONE;
 
 	switch (delta->status) {
 	case GIT_DELTA_UNMODIFIED: /* case 19 or 24 (or 34 but not really) */
-		if (checkout_notify(data, GIT_CHECKOUT_NOTIFY_DIRTY, delta, NULL) ||
-			checkout_notify(
-				data, GIT_CHECKOUT_NOTIFY_UNTRACKED, NULL, wd))
-			return GIT_EUSER;
+		GITERR_CHECK_ERROR(
+			checkout_notify(data, GIT_CHECKOUT_NOTIFY_DIRTY, delta, NULL));
+		GITERR_CHECK_ERROR(
+			checkout_notify(data, GIT_CHECKOUT_NOTIFY_UNTRACKED, NULL, wd));
 		break;
 	case GIT_DELTA_ADDED:/* case 4 (and 7 for dir) */
 	case GIT_DELTA_MODIFIED: /* case 20 (or 37 but not really) */
 		if (delta->old_file.mode == GIT_FILEMODE_COMMIT)
 			/* expected submodule (and maybe found one) */;
 		else if (delta->new_file.mode != GIT_FILEMODE_TREE)
-			action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
+			*action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
 		break;
 	case GIT_DELTA_DELETED: /* case 11 (and 27 for dir) */
-		if (delta->old_file.mode != GIT_FILEMODE_TREE &&
-			checkout_notify(
-				data, GIT_CHECKOUT_NOTIFY_UNTRACKED, NULL, wd))
-			return GIT_EUSER;
+		if (delta->old_file.mode != GIT_FILEMODE_TREE)
+			GITERR_CHECK_ERROR(
+				checkout_notify(data, GIT_CHECKOUT_NOTIFY_UNTRACKED, NULL, wd));
 		break;
 	case GIT_DELTA_TYPECHANGE: /* case 24 or 31 */
 		if (delta->old_file.mode == GIT_FILEMODE_TREE) {
@@ -462,39 +462,41 @@ static int checkout_action_with_wd_dir(
 			 * directory if is it left empty, so we can defer removing the
 			 * dir and it will succeed if no children are left.
 			 */
-			action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
-			if (action != CHECKOUT_ACTION__NONE)
-				action |= CHECKOUT_ACTION__DEFER_REMOVE;
+			*action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
+			if (*action != CHECKOUT_ACTION__NONE)
+				*action |= CHECKOUT_ACTION__DEFER_REMOVE;
 		}
 		else if (delta->new_file.mode != GIT_FILEMODE_TREE)
 			/* For typechange to dir, dir is already created so no action */
-			action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
+			*action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
 		break;
 	default: /* impossible */
 		break;
 	}
 
-	return checkout_action_common(data, action, delta, wd);
+	return checkout_action_common(action, data, delta, wd);
 }
 
 static int checkout_action(
+	int *action,
 	checkout_data *data,
 	git_diff_delta *delta,
 	git_iterator *workdir,
-	const git_index_entry **wditem_ptr,
+	const git_index_entry **wditem,
 	git_vector *pathspec)
 {
-	const git_index_entry *wd = *wditem_ptr;
-	int cmp = -1, act;
+	int cmp = -1, error;
 	int (*strcomp)(const char *, const char *) = data->diff->strcomp;
 	int (*pfxcomp)(const char *str, const char *pfx) = data->diff->pfxcomp;
-	int error;
+	int (*advance)(const git_index_entry **, git_iterator *) = NULL;
 
 	/* move workdir iterator to follow along with deltas */
 
 	while (1) {
+		const git_index_entry *wd = *wditem;
+
 		if (!wd)
-			return checkout_action_no_wd(data, delta);
+			return checkout_action_no_wd(action, data, delta);
 
 		cmp = strcomp(wd->path, delta->old_file.path);
 
@@ -512,79 +514,77 @@ static int checkout_action(
 			if (cmp == 0) {
 				if (wd->mode == GIT_FILEMODE_TREE) {
 					/* case 2 - entry prefixed by workdir tree */
-					error = git_iterator_advance_into_or_over(&wd, workdir);
-					if (error && error != GIT_ITEROVER)
-						goto fail;
-					*wditem_ptr = wd;
+					error = git_iterator_advance_into_or_over(wditem, workdir);
+					if (error < 0 && error != GIT_ITEROVER)
+						goto done;
 					continue;
 				}
 
 				/* case 3 maybe - wd contains non-dir where dir expected */
 				if (delta->old_file.path[strlen(wd->path)] == '/') {
-					act = checkout_action_with_wd_blocker(data, delta, wd);
-					*wditem_ptr =
-						git_iterator_advance(&wd, workdir) ? NULL : wd;
-					return act;
+					error = checkout_action_with_wd_blocker(
+						action, data, delta, wd);
+					advance = git_iterator_advance;
+					goto done;
 				}
 			}
 
 			/* case 1 - handle wd item (if it matches pathspec) */
-			if (checkout_action_wd_only(data, workdir, wd, pathspec) < 0)
-				goto fail;
-			if ((error = git_iterator_advance(&wd, workdir)) < 0 &&
+			error = checkout_action_wd_only(data, workdir, wd, pathspec);
+			if (error)
+				goto done;
+			if ((error = git_iterator_advance(wditem, workdir)) < 0 &&
 				error != GIT_ITEROVER)
-				goto fail;
-
-			*wditem_ptr = wd;
+				goto done;
 			continue;
 		}
 
 		if (cmp == 0) {
 			/* case 4 */
-			act = checkout_action_with_wd(data, delta, wd);
-			*wditem_ptr = git_iterator_advance(&wd, workdir) ? NULL : wd;
-			return act;
+			error = checkout_action_with_wd(action, data, delta, wd);
+			advance = git_iterator_advance;
+			goto done;
 		}
 
 		cmp = pfxcomp(wd->path, delta->old_file.path);
 
 		if (cmp == 0) { /* case 5 */
 			if (wd->path[strlen(delta->old_file.path)] != '/')
-				return checkout_action_no_wd(data, delta);
+				return checkout_action_no_wd(action, data, delta);
 
 			if (delta->status == GIT_DELTA_TYPECHANGE) {
 				if (delta->old_file.mode == GIT_FILEMODE_TREE) {
-					act = checkout_action_with_wd(data, delta, wd);
-					if ((error = git_iterator_advance_into(&wd, workdir)) < 0 &&
-						error != GIT_ENOTFOUND)
-						goto fail;
-					*wditem_ptr = wd;
-					return act;
+					error = checkout_action_with_wd(action, data, delta, wd);
+					advance = git_iterator_advance_into;
+					goto done;
 				}
 
 				if (delta->new_file.mode == GIT_FILEMODE_TREE ||
 					delta->new_file.mode == GIT_FILEMODE_COMMIT ||
 					delta->old_file.mode == GIT_FILEMODE_COMMIT)
 				{
-					act = checkout_action_with_wd(data, delta, wd);
-					if ((error = git_iterator_advance(&wd, workdir)) < 0 &&
-						error != GIT_ITEROVER)
-						goto fail;
-					*wditem_ptr = wd;
-					return act;
+					error = checkout_action_with_wd(action, data, delta, wd);
+					advance = git_iterator_advance;
+					goto done;
 				}
 			}
 
-			return checkout_action_with_wd_dir(data, delta, wd);
+			return checkout_action_with_wd_dir(action, data, delta, wd);
 		}
 
 		/* case 6 - wd is after delta */
-		return checkout_action_no_wd(data, delta);
+		return checkout_action_no_wd(action, data, delta);
 	}
 
-fail:
-	*wditem_ptr = NULL;
-	return -1;
+done:
+	if (!error && advance != NULL &&
+		(error = advance(wditem, workdir)) < 0) {
+		*wditem = NULL;
+		if (error == GIT_ITEROVER)
+			error = 0;
+	}
+
+	return error;
 }
 
 static int checkout_remaining_wd_items(
@@ -846,7 +846,7 @@ static int checkout_conflicts_coalesce_renames(
 
 	/* Juggle entries based on renames */
 	names = git_index_name_entrycount(data->index);
-	
+
 	for (i = 0; i < names; i++) {
 		name_entry = git_index_name_get_byindex(data->index, i);
 
@@ -965,7 +965,7 @@ static int checkout_get_actions(
 	checkout_data *data,
 	git_iterator *workdir)
 {
-	int error = 0;
+	int error = 0, act;
 	const git_index_entry *wditem;
 	git_vector pathspec = GIT_VECTOR_INIT, *deltas;
 	git_pool pathpool = GIT_POOL_INIT_STRINGPOOL;
@@ -992,12 +992,9 @@ static int checkout_get_actions(
 	}
 
 	git_vector_foreach(deltas, i, delta) {
-		int act = checkout_action(data, delta, workdir, &wditem, &pathspec);
-
-		if (act < 0) {
-			error = act;
+		error = checkout_action(&act, data, delta, workdir, &wditem, &pathspec);
+		if (error != 0)
 			goto fail;
-		}
 
 		actions[i] = act;
 
@@ -1012,7 +1009,7 @@ static int checkout_get_actions(
 	}
 
 	error = checkout_remaining_wd_items(data, workdir, wditem, &pathspec);
-	if (error < 0)
+	if (error)
 		goto fail;
 
 	counts[CHECKOUT_ACTION__REMOVE] += data->removes.length;
@@ -1760,9 +1757,6 @@ static int checkout_create_conflicts(checkout_data *data)
 
 static void checkout_data_clear(checkout_data *data)
 {
-	checkout_conflictdata *conflict;
-	size_t i;
-
 	if (data->opts_free_baseline) {
 		git_tree_free(data->opts.baseline);
 		data->opts.baseline = NULL;
@@ -1771,10 +1765,7 @@ static void checkout_data_clear(checkout_data *data)
 	git_vector_free(&data->removes);
 	git_pool_clear(&data->pool);
 
-	git_vector_foreach(&data->conflicts, i, conflict)
-		git__free(conflict);
-
-	git_vector_free(&data->conflicts);
+	git_vector_free_deep(&data->conflicts);
 
 	git__free(data->pfx);
 	data->pfx = NULL;
@@ -1966,7 +1957,7 @@ int git_checkout_iterator(
 	 * actions to be taken, plus look for conflicts and send notifications,
 	 * then loop through conflicts.
 	 */
-	if ((error = checkout_get_actions(&actions, &counts, &data, workdir)) < 0)
+	if ((error = checkout_get_actions(&actions, &counts, &data, workdir)) != 0)
 		goto cleanup;
 
 	data.total_steps = counts[CHECKOUT_ACTION__REMOVE] +
@@ -1998,9 +1989,6 @@ int git_checkout_iterator(
 	assert(data.completed_steps == data.total_steps);
 
 cleanup:
-	if (error == GIT_EUSER)
-		giterr_clear();
-
 	if (!error && data.index != NULL &&
 		(data.strategy & GIT_CHECKOUT_DONT_UPDATE_INDEX) == 0)
 		error = git_index_write(data.index);
diff --git a/src/clone.c b/src/clone.c
index 23aacd478..828c47ffb 100644
--- a/src/clone.c
+++ b/src/clone.c
@@ -115,43 +115,38 @@ static int reference_matches_remote_head(
 {
 	struct head_info *head_info = (struct head_info *)payload;
 	git_oid oid;
+	int error;
 
 	/* TODO: Should we guard against references
 	 * which name doesn't start with refs/heads/ ?
 	 */
 
-	/* Stop looking if we've already found a match */
-	if (head_info->found)
+	error = git_reference_name_to_id(&oid, head_info->repo, reference_name);
+	if (error == GIT_ENOTFOUND) {
+		/* If the reference doesn't exists, it obviously cannot match the
+		 * expected oid. */
+		giterr_clear();
 		return 0;
-
-	if (git_reference_name_to_id(
-		&oid,
-		head_info->repo,
-		reference_name) < 0) {
-			/* If the reference doesn't exists, it obviously cannot match the expected oid. */
-			giterr_clear();
-			return 0;
 	}
 
-	if (git_oid__cmp(&head_info->remote_head_oid, &oid) == 0) {
+	if (!error && !git_oid__cmp(&head_info->remote_head_oid, &oid)) {
 		/* Determine the local reference name from the remote tracking one */
-		if (git_refspec_transform_l(
-			&head_info->branchname,
-			head_info->refspec,
-			reference_name) < 0)
-				return -1;
-
-		if (git_buf_len(&head_info->branchname) > 0) {
-			if (git_buf_sets(
-				&head_info->branchname,
-				git_buf_cstr(&head_info->branchname) + strlen(GIT_REFS_HEADS_DIR)) < 0)
-					return -1;
+		error = git_refspec_transform_l(
+			&head_info->branchname, head_info->refspec, reference_name);
 
-			head_info->found = 1;
+		if (!error &&
+			git_buf_len(&head_info->branchname) > 0 &&
+			!(error = git_buf_sets(
+				&head_info->branchname,
+				git_buf_cstr(&head_info->branchname) +
+				strlen(GIT_REFS_HEADS_DIR))))
+		{
+			head_info->found = true;
+			error = GIT_ITEROVER;
 		}
 	}
 
-	return 0;
+	return error;
 }
 
 static int update_head_to_new_branch(
@@ -160,16 +155,11 @@ static int update_head_to_new_branch(
 	const char *name)
 {
 	git_reference *tracking_branch = NULL;
-	int error;
+	int error = create_tracking_branch(&tracking_branch, repo, target, name);
 
-	if ((error = create_tracking_branch(
-		&tracking_branch,
-		repo,
-		target,
-		name)) < 0)
-			return error;
-
-	error = git_repository_set_head(repo, git_reference_name(tracking_branch));
+	if (!error)
+		error = git_repository_set_head(
+			repo, git_reference_name(tracking_branch));
 
 	git_reference_free(tracking_branch);
 
@@ -178,34 +168,30 @@ static int update_head_to_new_branch(
 
 static int update_head_to_remote(git_repository *repo, git_remote *remote)
 {
-	int retcode = -1;
+	int error = 0;
 	size_t refs_len;
 	git_refspec dummy_spec;
 	const git_remote_head *remote_head, **refs;
 	struct head_info head_info;
 	git_buf remote_master_name = GIT_BUF_INIT;
 
-	if (git_remote_ls(&refs, &refs_len, remote) < 0)
-		return -1;
+	if ((error = git_remote_ls(&refs, &refs_len, remote)) < 0)
+		return error;
 
 	/* Did we just clone an empty repository? */
-	if (refs_len == 0) {
+	if (refs_len == 0)
 		return setup_tracking_config(
-			repo,
-			"master",
-			GIT_REMOTE_ORIGIN,
-			GIT_REFS_HEADS_MASTER_FILE);
-	}
+			repo, "master", GIT_REMOTE_ORIGIN, GIT_REFS_HEADS_MASTER_FILE);
 
 	/* Get the remote's HEAD. This is always the first ref in the list. */
 	remote_head = refs[0];
 	assert(remote_head);
 
+	memset(&head_info, 0, sizeof(head_info));
 	git_oid_cpy(&head_info.remote_head_oid, &remote_head->oid);
-	git_buf_init(&head_info.branchname, 16);
 	head_info.repo = repo;
-	head_info.refspec = git_remote__matching_refspec(remote, GIT_REFS_HEADS_MASTER_FILE);
-	head_info.found = 0;
+	head_info.refspec =
+		git_remote__matching_refspec(remote, GIT_REFS_HEADS_MASTER_FILE);
 
 	if (head_info.refspec == NULL) {
 		memset(&dummy_spec, 0, sizeof(git_refspec));
@@ -213,50 +199,46 @@ static int update_head_to_remote(git_repository *repo, git_remote *remote)
 	}
 
 	/* Determine the remote tracking reference name from the local master */
-	if (git_refspec_transform_r(
+	if ((error = git_refspec_transform_r(
 		&remote_master_name,
 		head_info.refspec,
-		GIT_REFS_HEADS_MASTER_FILE) < 0)
-			return -1;
+		GIT_REFS_HEADS_MASTER_FILE)) < 0)
+		return error;
 
 	/* Check to see if the remote HEAD points to the remote master */
-	if (reference_matches_remote_head(git_buf_cstr(&remote_master_name), &head_info) < 0)
+	error = reference_matches_remote_head(
+		git_buf_cstr(&remote_master_name), &head_info);
+	if (error < 0 && error != GIT_ITEROVER)
 		goto cleanup;
 
 	if (head_info.found) {
-		retcode = update_head_to_new_branch(
+		error = update_head_to_new_branch(
 			repo,
 			&head_info.remote_head_oid,
 			git_buf_cstr(&head_info.branchname));
-
 		goto cleanup;
 	}
 
 	/* Not master. Check all the other refs. */
-	if (git_reference_foreach_name(
-		repo,
-		reference_matches_remote_head,
-		&head_info) < 0)
-			goto cleanup;
+	error = git_reference_foreach_name(
+		repo, reference_matches_remote_head, &head_info);
+	if (error < 0 && error != GIT_ITEROVER)
+		goto cleanup;
 
 	if (head_info.found) {
-		retcode = update_head_to_new_branch(
+		error = update_head_to_new_branch(
 			repo,
 			&head_info.remote_head_oid,
 			git_buf_cstr(&head_info.branchname));
-
-		goto cleanup;
 	} else {
-		retcode = git_repository_set_head_detached(
-			repo,
-			&head_info.remote_head_oid);
-		goto cleanup;
+		error = git_repository_set_head_detached(
+			repo, &head_info.remote_head_oid);
 	}
 
 cleanup:
 	git_buf_free(&remote_master_name);
 	git_buf_free(&head_info.branchname);
-	return retcode;
+	return error;
 }
 
 static int update_head_to_branch(
@@ -359,7 +341,7 @@ int git_clone_into(git_repository *repo, git_remote *remote, const git_checkout_
 	old_fetchhead = git_remote_update_fetchhead(remote);
 	git_remote_set_update_fetchhead(remote, 0);
 
-	if ((error = git_remote_fetch(remote)) < 0)
+	if ((error = git_remote_fetch(remote)) != 0)
 		goto cleanup;
 
 	if (branch)
@@ -373,10 +355,12 @@ int git_clone_into(git_repository *repo, git_remote *remote, const git_checkout_
 
 cleanup:
 	git_remote_set_update_fetchhead(remote, old_fetchhead);
+
 	/* Go back to the original refspecs */
-	if (git_remote_set_fetch_refspecs(remote, &refspecs) < 0) {
-		git_strarray_free(&refspecs);
-		return -1;
+	{
+		int error_alt = git_remote_set_fetch_refspecs(remote, &refspecs);
+		if (!error)
+			error = error_alt;
 	}
 
 	git_strarray_free(&refspecs);
@@ -424,9 +408,10 @@ int git_clone(
 		git_remote_free(origin);
 	}
 
-	if (error < 0) {
+	if (error != 0) {
 		git_repository_free(repo);
 		repo = NULL;
+
 		(void)git_futils_rmdir_r(local_path, NULL, rmdir_flags);
 	}
 
diff --git a/src/common.h b/src/common.h
index a1888785e..e315b5979 100644
--- a/src/common.h
+++ b/src/common.h
@@ -62,7 +62,7 @@
  * Check a return value and propogate result if non-zero.
  */
 #define GITERR_CHECK_ERROR(code) \
-	do { int _err = (code); if (_err < 0) return _err; } while (0)
+	do { int _err = (code); if (_err) return _err; } while (0)
 
 /**
  * Set the error message for this thread, formatting as needed.
@@ -76,28 +76,61 @@ void giterr_set(int error_class, const char *string, ...);
 int giterr_set_regex(const regex_t *regex, int error_code);
 
 /**
- * Gets the system error code for this thread.
+ * Set error message for user callback if needed.
+ *
+ * If the error code in non-zero and no error message is set, this
+ * sets a generic error message.
+ *
+ * @return This always returns the `error_code` parameter.
  */
-GIT_INLINE(int) giterr_system_last(void)
+GIT_INLINE(int) giterr_set_after_callback_function(
+	int error_code, const char *action)
 {
+	if (error_code) {
+		const git_error *e = giterr_last();
+		if (!e || !e->message)
+			giterr_set(e ? e->klass : GITERR_CALLBACK,
+				"%s callback returned %d", action, error_code);
+	}
+	return error_code;
+}
+
 #ifdef GIT_WIN32
-	return GetLastError();
+#define giterr_set_after_callback(code) \
+	giterr_set_after_callback_function((code), __FUNCTION__)
 #else
-	return errno;
+#define giterr_set_after_callback(code) \
+	giterr_set_after_callback_function((code), __func__)
 #endif
-}
+
+/**
+ * Gets the system error code for this thread.
+ */
+int giterr_system_last(void);
 
 /**
  * Sets the system error code for this thread.
  */
-GIT_INLINE(void) giterr_system_set(int code)
-{
-#ifdef GIT_WIN32
-	SetLastError(code);
-#else
-	errno = code;
-#endif
-}
+void giterr_system_set(int code);
+
+/**
+ * Structure to preserve libgit2 error state
+ */
+typedef struct {
+	int       error_code;
+	git_error error_msg;
+} git_error_state;
+
+/**
+ * Capture current error state to restore later, returning error code.
+ * If `error_code` is zero, this does nothing and returns zero.
+ */
+int giterr_capture(git_error_state *state, int error_code);
+
+/**
+ * Restore error state to a previous value, returning saved error code.
+ */
+int giterr_restore(git_error_state *state);
 
 /**
  * Check a versioned structure for validity
diff --git a/src/config.c b/src/config.c
index 0d9471383..056a6ae13 100644
--- a/src/config.c
+++ b/src/config.c
@@ -480,47 +480,45 @@ int git_config_foreach(
 int git_config_backend_foreach_match(
 	git_config_backend *backend,
 	const char *regexp,
-	int (*fn)(const git_config_entry *, void *),
-	void *data)
+	git_config_foreach_cb cb,
+	void *payload)
 {
 	git_config_entry *entry;
 	git_config_iterator* iter;
 	regex_t regex;
-	int result = 0;
+	int error = 0;
 
 	if (regexp != NULL) {
-		if ((result = regcomp(&regex, regexp, REG_EXTENDED)) < 0) {
-			giterr_set_regex(&regex, result);
+		if ((error = regcomp(&regex, regexp, REG_EXTENDED)) < 0) {
+			giterr_set_regex(&regex, error);
 			regfree(&regex);
 			return -1;
 		}
 	}
 
-	if ((result = backend->iterator(&iter, backend)) < 0) {
+	if ((error = backend->iterator(&iter, backend)) < 0) {
 		iter = NULL;
 		return -1;
 	}
 
-	while(!(iter->next(&entry, iter) < 0)) {
+	while (!(iter->next(&entry, iter) < 0)) {
 		/* skip non-matching keys if regexp was provided */
 		if (regexp && regexec(&regex, entry->name, 0, NULL, 0) != 0)
 			continue;
 
 		/* abort iterator on non-zero return value */
-		if (fn(entry, data)) {
-			giterr_clear();
-			result = GIT_EUSER;
-			goto cleanup;
+		if ((error = cb(entry, payload)) != 0) {
+			giterr_set_after_callback(error);
+			break;
 		}
 	}
 
-cleanup:
 	if (regexp != NULL)
 		regfree(&regex);
 
 	iter->free(iter);
 
-	return result;
+	return error;
 }
 
 int git_config_foreach_match(
@@ -536,10 +534,9 @@ int git_config_foreach_match(
 	if ((error = git_config_iterator_glob_new(&iter, cfg, regexp)) < 0)
 		return error;
 
-	while ((error = git_config_next(&entry, iter)) == 0) {
-		if(cb(entry, payload)) {
-			giterr_clear();
-			error = GIT_EUSER;
+	while (!(error = git_config_next(&entry, iter))) {
+		if ((error = cb(entry, payload)) != 0) {
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
@@ -620,6 +617,78 @@ int git_config_set_string(git_config *cfg, const char *name, const char *value)
 /***********
  * Getters
  ***********/
+
+static int config_error_notfound(const char *name)
+{
+	giterr_set(GITERR_CONFIG, "Config value '%s' was not found", name);
+	return GIT_ENOTFOUND;
+}
+
+enum {
+	GET_ALL_ERRORS = 0,
+	GET_NO_MISSING = 1,
+	GET_NO_ERRORS  = 2
+};
+
+static int get_entry(
+	const git_config_entry **out,
+	const git_config *cfg,
+	const char *name,
+	bool normalize_name,
+	int want_errors)
+{
+	int res = GIT_ENOTFOUND;
+	const char *key = name;
+	char *normalized = NULL;
+	size_t i;
+	file_internal *internal;
+
+	*out = NULL;
+
+	if (normalize_name) {
+		if ((res = git_config__normalize_name(name, &normalized)) < 0)
+			goto cleanup;
+		key = normalized;
+	}
+
+	git_vector_foreach(&cfg->files, i, internal) {
+		if (!internal || !internal->file)
+			continue;
+
+		res = internal->file->get(internal->file, key, out);
+		if (res != GIT_ENOTFOUND)
+			break;
+	}
+
+	git__free(normalized);
+
+cleanup:
+	if (res == GIT_ENOTFOUND)
+		res = (want_errors > GET_ALL_ERRORS) ? 0 : config_error_notfound(name);
+	else if (res && (want_errors == GET_NO_ERRORS)) {
+		giterr_clear();
+		res = 0;
+	}
+
+	return res;
+}
+
+int git_config_get_entry(
+	const git_config_entry **out, const git_config *cfg, const char *name)
+{
+	return get_entry(out, cfg, name, true, GET_ALL_ERRORS);
+}
+
+int git_config__lookup_entry(
+	const git_config_entry **out,
+	const git_config *cfg,
+	const char *key,
+	bool no_errors)
+{
+	return get_entry(
+		out, cfg, key, false, no_errors ? GET_NO_ERRORS : GET_NO_MISSING);
+}
+
 int git_config_get_mapped(
 	int *out,
 	const git_config *cfg,
@@ -627,116 +696,91 @@ int git_config_get_mapped(
 	const git_cvar_map *maps,
 	size_t map_n)
 {
-	const char *value;
+	const git_config_entry *entry;
 	int ret;
 
-	if ((ret = git_config_get_string(&value, cfg, name)) < 0)
+	if ((ret = get_entry(&entry, cfg, name, true, GET_ALL_ERRORS)) < 0)
 		return ret;
 
-	return git_config_lookup_map_value(out, maps, map_n, value);
+	return git_config_lookup_map_value(out, maps, map_n, entry->value);
 }
 
 int git_config_get_int64(int64_t *out, const git_config *cfg, const char *name)
 {
-	const char *value;
+	const git_config_entry *entry;
 	int ret;
 
-	if ((ret = git_config_get_string(&value, cfg, name)) < 0)
+	if ((ret = get_entry(&entry, cfg, name, true, GET_ALL_ERRORS)) < 0)
 		return ret;
 
-	return git_config_parse_int64(out, value);
+	return git_config_parse_int64(out, entry->value);
 }
 
 int git_config_get_int32(int32_t *out, const git_config *cfg, const char *name)
 {
-	const char *value;
+	const git_config_entry *entry;
 	int ret;
 
-	if ((ret = git_config_get_string(&value, cfg, name)) < 0)
+	if ((ret = get_entry(&entry, cfg, name, true, GET_ALL_ERRORS)) < 0)
 		return ret;
 
-	return git_config_parse_int32(out, value);
+	return git_config_parse_int32(out, entry->value);
 }
 
-static int get_string_at_file(const char **out, const git_config_backend *file, const char *name)
+int git_config_get_bool(int *out, const git_config *cfg, const char *name)
 {
 	const git_config_entry *entry;
-	int res;
+	int ret;
 
-	res = file->get(file, name, &entry);
-	if (!res)
-		*out = entry->value;
+	if ((ret = get_entry(&entry, cfg, name, true, GET_ALL_ERRORS)) < 0)
+		return ret;
 
-	return res;
+	return git_config_parse_bool(out, entry->value);
 }
 
-static int config_error_notfound(const char *name)
+int git_config_get_string(
+	const char **out, const git_config *cfg, const char *name)
 {
-	giterr_set(GITERR_CONFIG, "Config value '%s' was not found", name);
-	return GIT_ENOTFOUND;
+	const git_config_entry *entry;
+	int ret = get_entry(&entry, cfg, name, true, GET_ALL_ERRORS);
+	*out = !ret ? (entry->value ? entry->value : "") : NULL;
+	return ret;
 }
 
-static int get_string(const char **out, const git_config *cfg, const char *name)
+const char *git_config__get_string_force(
+	const git_config *cfg, const char *key, const char *fallback_value)
 {
-	file_internal *internal;
-	unsigned int i;
-	int res;
-
-	git_vector_foreach(&cfg->files, i, internal) {
-		if (!internal || !internal->file)
-			continue;
-
-		res = get_string_at_file(out, internal->file, name);
-		if (res != GIT_ENOTFOUND)
-			return res;
-	}
-
-	return config_error_notfound(name);
+	const git_config_entry *entry;
+	get_entry(&entry, cfg, key, false, GET_NO_ERRORS);
+	return (entry && entry->value) ? entry->value : fallback_value;
 }
 
-int git_config_get_bool(int *out, const git_config *cfg, const char *name)
+int git_config__get_bool_force(
+	const git_config *cfg, const char *key, int fallback_value)
 {
-	const char *value = NULL;
-	int ret;
-
-	if ((ret = get_string(&value, cfg, name)) < 0)
-		return ret;
-
-	return git_config_parse_bool(out, value);
-}
+	int val = fallback_value;
+	const git_config_entry *entry;
 
-int git_config_get_string(const char **out, const git_config *cfg, const char *name)
-{
-	int ret;
-	const char *str = NULL;
+	get_entry(&entry, cfg, key, false, GET_NO_ERRORS);
 
-	if ((ret = get_string(&str, cfg, name)) < 0)
-		return ret;
+	if (entry && git_config_parse_bool(&val, entry->value) < 0)
+		giterr_clear();
 
-	*out = str == NULL ? "" : str;
-	return 0;
+	return val;
 }
 
-int git_config_get_entry(const git_config_entry **out, const git_config *cfg, const char *name)
+int git_config__get_int_force(
+	const git_config *cfg, const char *key, int fallback_value)
 {
-	file_internal *internal;
-	unsigned int i;
-	git_config_backend *file;
-	int ret;
-
-	*out = NULL;
+	int32_t val = (int32_t)fallback_value;
+	const git_config_entry *entry;
 
-	git_vector_foreach(&cfg->files, i, internal) {
-		if (!internal || !internal->file)
-			continue;
-		file = internal->file;
+	get_entry(&entry, cfg, key, false, GET_NO_ERRORS);
 
-		ret = file->get(file, name, out);
-		if (ret != GIT_ENOTFOUND)
-			return ret;
-	}
+	if (entry && git_config_parse_int32(&val, entry->value) < 0)
+		giterr_clear();
 
-	return config_error_notfound(name);
+	return (int)val;
 }
 
 int git_config_get_multivar_foreach(
@@ -753,9 +797,10 @@ int git_config_get_multivar_foreach(
 	found = 0;
 	while ((err = iter->next(&entry, iter)) == 0) {
 		found = 1;
-		if(cb(entry, payload)) {
-			iter->free(iter);
-			return GIT_EUSER;
+
+		if ((err = cb(entry, payload)) != 0) {
+			giterr_set_after_callback(err);
+			break;
 		}
 	}
 
@@ -1070,7 +1115,7 @@ int git_config_parse_int64(int64_t *out, const char *value)
 	const char *num_end;
 	int64_t num;
 
-	if (git__strtol64(&num, value, &num_end, 0) < 0)
+	if (!value || git__strtol64(&num, value, &num_end, 0) < 0)
 		goto fail_parse;
 
 	switch (*num_end) {
@@ -1167,7 +1212,6 @@ struct rename_data {
 	git_config *config;
 	git_buf *name;
 	size_t old_len;
-	int actual_error;
 };
 
 static int rename_config_entries_cb(
@@ -1190,8 +1234,6 @@ static int rename_config_entries_cb(
 	if (!error)
 		error = git_config_delete_entry(data->config, entry->name);
 
-	data->actual_error = error; /* preserve actual error code */
-
 	return error;
 }
 
@@ -1216,7 +1258,6 @@ int git_config_rename_section(
 	data.config  = config;
 	data.name    = &replace;
 	data.old_len = strlen(old_section_name) + 1;
-	data.actual_error = 0;
 
 	if ((error = git_buf_join(&replace, '.', new_section_name, "")) < 0)
 		goto cleanup;
@@ -1233,9 +1274,6 @@ int git_config_rename_section(
 	error = git_config_foreach_match(
 		config, git_buf_cstr(&pattern), rename_config_entries_cb, &data);
 
-	if (error == GIT_EUSER)
-		error = data.actual_error;
-
 cleanup:
 	git_buf_free(&pattern);
 	git_buf_free(&replace);
diff --git a/src/config.h b/src/config.h
index 01e8465cc..3cd888c88 100644
--- a/src/config.h
+++ b/src/config.h
@@ -51,5 +51,26 @@ extern int git_config_file__ondisk(git_config_backend **out, const char *path);
 
 extern int git_config__normalize_name(const char *in, char **out);
 
+/* internal only: does not normalize key and sets out to NULL if not found */
+extern int git_config__lookup_entry(
+	const git_config_entry **out,
+	const git_config *cfg,
+	const char *key,
+	bool no_errors);
+
+/*
+ * Lookup functions that cannot fail.  These functions look up a config
+ * value and return a fallback value if the value is missing or if any
+ * failures occur while trying to access the value.
+ */
+
+extern const char *git_config__get_string_force(
+	const git_config *cfg, const char *key, const char *fallback_value);
+
+extern int git_config__get_bool_force(
+	const git_config *cfg, const char *key, int fallback_value);
+
+extern int git_config__get_int_force(
+	const git_config *cfg, const char *key, int fallback_value);
 
 #endif
diff --git a/src/config_cache.c b/src/config_cache.c
index 6808521a3..ec75d1501 100644
--- a/src/config_cache.c
+++ b/src/config_cache.c
@@ -78,22 +78,22 @@ int git_repository__cvar(int *out, git_repository *repo, git_cvar_cached cvar)
 		struct map_data *data = &_cvar_maps[(int)cvar];
 		git_config *config;
 		int error;
+		const git_config_entry *entry;
 
-		error = git_repository_config__weakptr(&config, repo);
-		if (error < 0)
+		if ((error = git_repository_config__weakptr(&config, repo)) < 0)
 			return error;
 
-		if (data->maps)
-			error = git_config_get_mapped(
-				out, config, data->cvar_name, data->maps, data->map_count);
-		else
-			error = git_config_get_bool(out, config, data->cvar_name);
+		git_config__lookup_entry(&entry, config, data->cvar_name, false);
 
-		if (error == GIT_ENOTFOUND) {
-			giterr_clear();
+		if (!entry)
 			*out = data->default_value;
-		}
-		else if (error < 0)
+		else if (data->maps)
+			error = git_config_lookup_map_value(
+				out, data->maps, data->map_count, entry->value);
+		else
+			error = git_config_parse_bool(out, entry->value);
+
+		if (error < 0)
 			return error;
 
 		repo->cvar_cache[(int)cvar] = *out;
diff --git a/src/config_file.c b/src/config_file.c
index 15c8de49c..0971aa7b0 100644
--- a/src/config_file.c
+++ b/src/config_file.c
@@ -404,20 +404,12 @@ static int config_set(git_config_backend *cfg, const char *name, const char *val
 /*
  * Internal function that actually gets the value in string form
  */
-static int config_get(const git_config_backend *cfg, const char *name, const git_config_entry **out)
+static int config_get(const git_config_backend *cfg, const char *key, const git_config_entry **out)
 {
 	diskfile_backend *b = (diskfile_backend *)cfg;
-	char *key;
-	khiter_t pos;
-	int error;
+	khiter_t pos = git_strmap_lookup_index(b->values, key);
 	cvar_t *var;
 
-	if ((error = git_config__normalize_name(name, &key)) < 0)
-		return error;
-
-	pos = git_strmap_lookup_index(b->values, key);
-	git__free(key);
-
 	/* no error message; the config system will write one */
 	if (!git_strmap_valid_index(b->values, pos))
 		return GIT_ENOTFOUND;
@@ -427,7 +419,6 @@ static int config_get(const git_config_backend *cfg, const char *name, const git
 		var = var->next;
 
 	*out = var->entry;
-
 	return 0;
 }
 
diff --git a/src/diff.c b/src/diff.c
index 4c33a0213..7f2e58c0c 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -49,16 +49,29 @@ static git_diff_delta *diff_delta__alloc(
 	return delta;
 }
 
-static int diff_notify(
-	const git_diff *diff,
-	const git_diff_delta *delta,
-	const char *matched_pathspec)
+static int diff_insert_delta(
+	git_diff *diff, git_diff_delta *delta, const char *matched_pathspec)
 {
-	if (!diff->opts.notify_cb)
-		return 0;
+	int error = 0;
+
+	if (diff->opts.notify_cb) {
+		error = diff->opts.notify_cb(
+			diff, delta, matched_pathspec, diff->opts.notify_payload);
+
+		if (error) {
+			git__free(delta);
+
+			if (error > 0)	/* positive value means to skip this delta */
+				return 0;
+			else			/* negative value means to cancel diff */
+				return giterr_set_after_callback_function(error, "git_diff");
+		}
+	}
+
+	if ((error = git_vector_insert(&diff->deltas, delta)) < 0)
+		git__free(delta);
 
-	return diff->opts.notify_cb(
-		diff, delta, matched_pathspec, diff->opts.notify_payload);
+	return error;
 }
 
 static int diff_delta__from_one(
@@ -68,7 +81,6 @@ static int diff_delta__from_one(
 {
 	git_diff_delta *delta;
 	const char *matched_pathspec;
-	int notify_res;
 
 	if ((entry->flags & GIT_IDXENTRY_VALID) != 0)
 		return 0;
@@ -111,21 +123,12 @@ static int diff_delta__from_one(
 		!git_oid_iszero(&delta->new_file.oid))
 		delta->new_file.flags |= GIT_DIFF_FLAG_VALID_OID;
 
-	notify_res = diff_notify(diff, delta, matched_pathspec);
-
-	if (notify_res)
-		git__free(delta);
-	else if (git_vector_insert(&diff->deltas, delta) < 0) {
-		git__free(delta);
-		return -1;
-	}
-
-	return notify_res < 0 ? GIT_EUSER : 0;
+	return diff_insert_delta(diff, delta, matched_pathspec);
 }
 
 static int diff_delta__from_two(
 	git_diff *diff,
-	git_delta_t   status,
+	git_delta_t status,
 	const git_index_entry *old_entry,
 	uint32_t old_mode,
 	const git_index_entry *new_entry,
@@ -134,7 +137,6 @@ static int diff_delta__from_two(
 	const char *matched_pathspec)
 {
 	git_diff_delta *delta;
-	int notify_res;
 	const char *canonical_path = old_entry->path;
 
 	if (status == GIT_DELTA_UNMODIFIED &&
@@ -173,16 +175,7 @@ static int diff_delta__from_two(
 	if (new_oid || !git_oid_iszero(&new_entry->oid))
 		delta->new_file.flags |= GIT_DIFF_FLAG_VALID_OID;
 
-	notify_res = diff_notify(diff, delta, matched_pathspec);
-
-	if (notify_res)
-		git__free(delta);
-	else if (git_vector_insert(&diff->deltas, delta) < 0) {
-		git__free(delta);
-		return -1;
-	}
-
-	return notify_res < 0 ? GIT_EUSER : 0;
+	return diff_insert_delta(diff, delta, matched_pathspec);
 }
 
 static git_diff_delta *diff_delta__last_for_item(
@@ -304,26 +297,6 @@ bool git_diff_delta__should_skip(
 }
 
 
-static int config_bool(git_config *cfg, const char *name, int defvalue)
-{
-	int val = defvalue;
-
-	if (git_config_get_bool(&val, cfg, name) < 0)
-		giterr_clear();
-
-	return val;
-}
-
-static int config_int(git_config *cfg, const char *name, int defvalue)
-{
-	int val = defvalue;
-
-	if (git_config_get_int32(&val, cfg, name) < 0)
-		giterr_clear();
-
-	return val;
-}
-
 static const char *diff_mnemonic_prefix(
 	git_iterator_type_t type, bool left_side)
 {
@@ -422,8 +395,8 @@ static int diff_list_apply_options(
 		diff->opts.flags |= GIT_DIFF_INCLUDE_UNTRACKED;
 
 	/* load config values that affect diff behavior */
-	if (git_repository_config__weakptr(&cfg, repo) < 0)
-		return -1;
+	if ((val = git_repository_config__weakptr(&cfg, repo)) < 0)
+		return val;
 
 	if (!git_repository__cvar(&val, repo, GIT_CVAR_SYMLINKS) && val)
 		diff->diffcaps = diff->diffcaps | GIT_DIFFCAPS_HAS_SYMLINKS;
@@ -445,7 +418,7 @@ static int diff_list_apply_options(
 
 	/* If not given explicit `opts`, check `diff.xyz` configs */
 	if (!opts) {
-		int context = config_int(cfg, "diff.context", 3);
+		int context = git_config__get_int_force(cfg, "diff.context", 3);
 		diff->opts.context_lines = context >= 0 ? (uint16_t)context : 3;
 
 		/* add other defaults here */
@@ -460,12 +433,11 @@ static int diff_list_apply_options(
 
 	/* if ignore_submodules not explicitly set, check diff config */
 	if (diff->opts.ignore_submodules <= 0) {
-		const char *str;
+		const git_config_entry *entry;
+		git_config__lookup_entry(&entry, cfg, "diff.ignoresubmodules", true);
 
-		if (git_config_get_string(&str , cfg, "diff.ignoreSubmodules") < 0)
-			giterr_clear();
-		else if (str != NULL &&
-			git_submodule_parse_ignore(&diff->opts.ignore_submodules, str) < 0)
+		if (entry && git_submodule_parse_ignore(
+				&diff->opts.ignore_submodules, entry->value) < 0)
 			giterr_clear();
 	}
 
@@ -474,9 +446,9 @@ static int diff_list_apply_options(
 		const char *use_old = DIFF_OLD_PREFIX_DEFAULT;
 		const char *use_new = DIFF_NEW_PREFIX_DEFAULT;
 
-		if (config_bool(cfg, "diff.noprefix", 0)) {
+		if (git_config__get_bool_force(cfg, "diff.noprefix", 0))
 			use_old = use_new = "";
-		} else if (config_bool(cfg, "diff.mnemonicprefix", 0)) {
+		else if (git_config__get_bool_force(cfg, "diff.mnemonicprefix", 0)) {
 			use_old = diff_mnemonic_prefix(diff->old_src, true);
 			use_new = diff_mnemonic_prefix(diff->new_src, false);
 		}
@@ -504,14 +476,7 @@ static int diff_list_apply_options(
 
 static void diff_list_free(git_diff *diff)
 {
-	git_diff_delta *delta;
-	unsigned int i;
-
-	git_vector_foreach(&diff->deltas, i, delta) {
-		git__free(delta);
-		diff->deltas.contents[i] = NULL;
-	}
-	git_vector_free(&diff->deltas);
+	git_vector_free_deep(&diff->deltas);
 
 	git_pathspec__vfree(&diff->pathspec);
 	git_pool_clear(&diff->pool);
@@ -682,6 +647,7 @@ static int maybe_modified(
 	unsigned int nmode = nitem->mode;
 	bool new_is_workdir = (info->new_iter->type == GIT_ITERATOR_TYPE_WORKDIR);
 	const char *matched_pathspec;
+	int error = 0;
 
 	if (!git_pathspec__match(
 			&diff->pathspec, oitem->path,
@@ -716,10 +682,9 @@ static int maybe_modified(
 		if (DIFF_FLAG_IS_SET(diff, GIT_DIFF_INCLUDE_TYPECHANGE))
 			status = GIT_DELTA_TYPECHANGE;
 		else {
-			if (diff_delta__from_one(diff, GIT_DELTA_DELETED, oitem) < 0 ||
-				diff_delta__from_one(diff, GIT_DELTA_ADDED, nitem) < 0)
-				return -1;
-			return 0;
+			if (!(error = diff_delta__from_one(diff, GIT_DELTA_DELETED, oitem)))
+				error = diff_delta__from_one(diff, GIT_DELTA_ADDED, nitem);
+			return error;
 		}
 	}
 
@@ -741,8 +706,8 @@ static int maybe_modified(
 		/* TODO: add check against index file st_mtime to avoid racy-git */
 
 		if (S_ISGITLINK(nmode)) {
-			if (maybe_modified_submodule(&status, &noid, diff, info) < 0)
-				return -1;
+			if ((error = maybe_modified_submodule(&status, &noid, diff, info)) < 0)
+				return error;
 		}
 
 		/* if the stat data looks different, then mark modified - this just
@@ -769,9 +734,9 @@ static int maybe_modified(
 	 */
 	if (status == GIT_DELTA_MODIFIED && git_oid_iszero(&nitem->oid)) {
 		if (git_oid_iszero(&noid)) {
-			if (git_diff__oid_for_file(diff->repo,
-					nitem->path, nitem->mode, nitem->file_size, &noid) < 0)
-				return -1;
+			if ((error = git_diff__oid_for_file(diff->repo,
+					nitem->path, nitem->mode, nitem->file_size, &noid)) < 0)
+				return error;
 		}
 
 		/* if oid matches, then mark unmodified (except submodules, where
@@ -926,7 +891,7 @@ static int handle_unmatched_new_item(
 			git_diff_delta *last;
 
 			/* attempt to insert record for this directory */
-			if ((error = diff_delta__from_one(diff, delta_type, nitem)) < 0)
+			if ((error = diff_delta__from_one(diff, delta_type, nitem)) != 0)
 				return error;
 
 			/* if delta wasn't created (because of rules), just skip ahead */
@@ -1005,7 +970,7 @@ static int handle_unmatched_new_item(
 	}
 
 	/* Actually create the record for this item if necessary */
-	if ((error = diff_delta__from_one(diff, delta_type, nitem)) < 0)
+	if ((error = diff_delta__from_one(diff, delta_type, nitem)) != 0)
 		return error;
 
 	/* If user requested TYPECHANGE records, then check for that instead of
@@ -1030,7 +995,7 @@ static int handle_unmatched_old_item(
 	git_diff *diff, diff_in_progress *info)
 {
 	int error = diff_delta__from_one(diff, GIT_DELTA_DELETED, info->oitem);
-	if (error < 0)
+	if (error != 0)
 		return error;
 
 	/* if we are generating TYPECHANGE records then check for that
@@ -1364,7 +1329,7 @@ int git_diff__paired_foreach(
 	int (*cb)(git_diff_delta *h2i, git_diff_delta *i2w, void *payload),
 	void *payload)
 {
-	int cmp;
+	int cmp, error = 0;
 	git_diff_delta *h2i, *i2w;
 	size_t i, j, i_max, j_max;
 	int (*strcomp)(const char *, const char *) = git__strcmp;
@@ -1420,18 +1385,17 @@ int git_diff__paired_foreach(
 			strcomp(h2i->new_file.path, i2w->old_file.path);
 
 		if (cmp < 0) {
-			if (cb(h2i, NULL, payload))
-				return GIT_EUSER;
-			i++;
+			i++; i2w = NULL;
 		} else if (cmp > 0) {
-			if (cb(NULL, i2w, payload))
-				return GIT_EUSER;
-			j++;
+			j++; h2i = NULL;
 		} else {
-			if (cb(h2i, i2w, payload))
-				return GIT_EUSER;
 			i++; j++;
 		}
+
+		if ((error = cb(h2i, i2w, payload)) != 0) {
+			giterr_set_after_callback(error);
+			break;
+		}
 	}
 
 	/* restore case-insensitive delta sort */
@@ -1447,5 +1411,5 @@ int git_diff__paired_foreach(
 		git_vector_sort(&idx2wd->deltas);
 	}
 
-	return 0;
+	return error;
 }
diff --git a/src/diff_driver.c b/src/diff_driver.c
index bd5a8fbd9..167c0cc5a 100644
--- a/src/diff_driver.c
+++ b/src/diff_driver.c
@@ -14,6 +14,7 @@
 #include "strmap.h"
 #include "map.h"
 #include "buf_text.h"
+#include "config.h"
 #include "repository.h"
 
 GIT__USE_STRMAP;
@@ -130,14 +131,14 @@ static git_diff_driver_registry *git_repository_driver_registry(
 static int git_diff_driver_load(
 	git_diff_driver **out, git_repository *repo, const char *driver_name)
 {
-	int error = 0, bval;
+	int error = 0;
 	git_diff_driver_registry *reg;
 	git_diff_driver *drv;
 	size_t namelen = strlen(driver_name);
 	khiter_t pos;
 	git_config *cfg;
 	git_buf name = GIT_BUF_INIT;
-	const char *val;
+	const git_config_entry *ce;
 	bool found_driver = false;
 
 	reg = git_repository_driver_registry(repo);
@@ -164,23 +165,21 @@ static int git_diff_driver_load(
 
 	if ((error = git_buf_printf(&name, "diff.%s.binary", driver_name)) < 0)
 		goto done;
-	if ((error = git_config_get_string(&val, cfg, name.ptr)) < 0) {
-		if (error != GIT_ENOTFOUND)
-			goto done;
-		/* diff.<driver>.binary unspecified, so just continue */
-		giterr_clear();
-	} else if (git_config_parse_bool(&bval, val) < 0) {
-		/* TODO: warn that diff.<driver>.binary has invalid value */
-		giterr_clear();
-	} else if (bval) {
+
+	switch (git_config__get_bool_force(cfg, name.ptr, -1)) {
+	case true:
 		/* if diff.<driver>.binary is true, just return the binary driver */
 		*out = &global_drivers[DIFF_DRIVER_BINARY];
 		goto done;
-	} else {
+	case false:
 		/* if diff.<driver>.binary is false, force binary checks off */
 		/* but still may have custom function context patterns, etc. */
 		drv->binary_flags = GIT_DIFF_FORCE_TEXT;
 		found_driver = true;
+		break;
+	default:
+		/* diff.<driver>.binary unspecified, so just continue */
+		break;
 	}
 
 	/* TODO: warn if diff.<name>.command or diff.<name>.textconv are set */
@@ -211,16 +210,16 @@ static int git_diff_driver_load(
 
 	git_buf_truncate(&name, namelen + strlen("diff.."));
 	git_buf_put(&name, "wordregex", strlen("wordregex"));
-	if ((error = git_config_get_string(&val, cfg, name.ptr)) < 0) {
-		if (error != GIT_ENOTFOUND)
-			goto done;
-		giterr_clear(); /* no diff.<driver>.wordregex, so just continue */
-	} else if ((error = regcomp(&drv->word_pattern, val, REG_EXTENDED)) != 0) {
-		/* TODO: warning about bad regex instead of failure */
-		error = giterr_set_regex(&drv->word_pattern, error);
+	if ((error = git_config__lookup_entry(&ce, cfg, name.ptr, false)) < 0)
 		goto done;
-	} else {
+	if (!ce || !ce->value)
+		/* no diff.<driver>.wordregex, so just continue */;
+	else if (!(error = regcomp(&drv->word_pattern, ce->value, REG_EXTENDED)))
 		found_driver = true;
+	else {
+		/* TODO: warn about bad regex instead of failure */
+		error = giterr_set_regex(&drv->word_pattern, error);
+		goto done;
 	}
 
 	/* TODO: look up diff.<driver>.algorithm to turn on minimal / patience
diff --git a/src/diff_patch.c b/src/diff_patch.c
index cc49d68eb..9c2eb885f 100644
--- a/src/diff_patch.c
+++ b/src/diff_patch.c
@@ -193,21 +193,18 @@ cleanup:
 	return error;
 }
 
-static int diff_patch_file_callback(
+static int diff_patch_invoke_file_callback(
 	git_patch *patch, git_diff_output *output)
 {
-	float progress;
+	float progress = patch->diff ?
+		((float)patch->delta_index / patch->diff->deltas.length) : 1.0f;
 
 	if (!output->file_cb)
 		return 0;
 
-	progress = patch->diff ?
-		((float)patch->delta_index / patch->diff->deltas.length) : 1.0f;
-
-	if (output->file_cb(patch->delta, progress, output->payload) != 0)
-		output->error = GIT_EUSER;
-
-	return output->error;
+	return giterr_set_after_callback_function(
+		output->file_cb(patch->delta, progress, output->payload),
+		"git_patch");
 }
 
 static int diff_patch_generate(git_patch *patch, git_diff_output *output)
@@ -229,7 +226,7 @@ static int diff_patch_generate(git_patch *patch, git_diff_output *output)
 		return 0;
 
 	if (output->diff_cb != NULL &&
-		!(error = output->diff_cb(output, patch)))
+		(error = output->diff_cb(output, patch)) < 0)
 		patch->flags |= GIT_DIFF_PATCH_DIFFED;
 
 	return error;
@@ -272,9 +269,10 @@ int git_diff_foreach(
 	size_t idx;
 	git_patch patch;
 
-	if (diff_required(diff, "git_diff_foreach") < 0)
-		return -1;
+	if ((error = diff_required(diff, "git_diff_foreach")) < 0)
+		return error;
 
+	memset(&xo, 0, sizeof(xo));
 	diff_output_init(
 		&xo.output, &diff->opts, file_cb, hunk_cb, data_cb, payload);
 	git_xdiff_init(&xo, &diff->opts);
@@ -285,22 +283,18 @@ int git_diff_foreach(
 		if (git_diff_delta__should_skip(&diff->opts, patch.delta))
 			continue;
 
-		if (!(error = diff_patch_init_from_diff(&patch, diff, idx))) {
+		if ((error = diff_patch_init_from_diff(&patch, diff, idx)) < 0)
+			break;
 
-			error = diff_patch_file_callback(&patch, &xo.output);
+		if (!(error = diff_patch_invoke_file_callback(&patch, &xo.output)))
+			error = diff_patch_generate(&patch, &xo.output);
 
-			if (!error)
-				error = diff_patch_generate(&patch, &xo.output);
+		git_patch_free(&patch);
 
-			git_patch_free(&patch);
-		}
-
-		if (error < 0)
+		if (error)
 			break;
 	}
 
-	if (error == GIT_EUSER)
-		giterr_clear(); /* don't leave error message set invalidly */
 	return error;
 }
 
@@ -332,14 +326,11 @@ static int diff_single_generate(diff_patch_with_delta *pd, git_xdiff_output *xo)
 		!(patch->ofile.opts_flags & GIT_DIFF_INCLUDE_UNMODIFIED))
 		return error;
 
-	error = diff_patch_file_callback(patch, (git_diff_output *)xo);
+	error = diff_patch_invoke_file_callback(patch, (git_diff_output *)xo);
 
 	if (!error)
 		error = diff_patch_generate(patch, (git_diff_output *)xo);
 
-	if (error == GIT_EUSER)
-		giterr_clear(); /* don't leave error message set invalidly */
-
 	return error;
 }
 
@@ -424,9 +415,7 @@ int git_diff_blobs(
 	diff_patch_with_delta pd;
 	git_xdiff_output xo;
 
-	memset(&pd, 0, sizeof(pd));
 	memset(&xo, 0, sizeof(xo));
-
 	diff_output_init(
 		&xo.output, opts, file_cb, hunk_cb, data_cb, payload);
 	git_xdiff_init(&xo, opts);
@@ -436,6 +425,7 @@ int git_diff_blobs(
 	else if (!new_path && old_path)
 		new_path = old_path;
 
+	memset(&pd, 0, sizeof(pd));
 	error = diff_patch_from_blobs(
 		&pd, &xo, old_blob, old_path, new_blob, new_path, opts);
 
@@ -463,7 +453,6 @@ int git_patch_from_blobs(
 		return -1;
 
 	memset(&xo, 0, sizeof(xo));
-
 	diff_output_to_patch(&xo.output, &pd->patch);
 	git_xdiff_init(&xo, opts);
 
@@ -536,9 +525,7 @@ int git_diff_blob_to_buffer(
 	diff_patch_with_delta pd;
 	git_xdiff_output xo;
 
-	memset(&pd, 0, sizeof(pd));
 	memset(&xo, 0, sizeof(xo));
-
 	diff_output_init(
 		&xo.output, opts, file_cb, hunk_cb, data_cb, payload);
 	git_xdiff_init(&xo, opts);
@@ -548,6 +535,7 @@ int git_diff_blob_to_buffer(
 	else if (!buf_path && old_path)
 		buf_path = old_path;
 
+	memset(&pd, 0, sizeof(pd));
 	error = diff_patch_from_blob_and_buffer(
 		&pd, &xo, old_blob, old_path, buf, buflen, buf_path, opts);
 
@@ -576,7 +564,6 @@ int git_patch_from_blob_and_buffer(
 		return -1;
 
 	memset(&xo, 0, sizeof(xo));
-
 	diff_output_to_patch(&xo.output, &pd->patch);
 	git_xdiff_init(&xo, opts);
 
@@ -622,17 +609,18 @@ int git_patch_from_diff(
 	if ((error = diff_patch_alloc_from_diff(&patch, diff, idx)) < 0)
 		return error;
 
+	memset(&xo, 0, sizeof(xo));
 	diff_output_to_patch(&xo.output, patch);
 	git_xdiff_init(&xo, &diff->opts);
 
-	error = diff_patch_file_callback(patch, &xo.output);
+	error = diff_patch_invoke_file_callback(patch, &xo.output);
 
 	if (!error)
 		error = diff_patch_generate(patch, &xo.output);
 
 	if (!error) {
-		/* if cumulative diff size is < 0.5 total size, flatten the patch */
-		/* unload the file content */
+		/* TODO: if cumulative diff size is < 0.5 total size, flatten patch */
+		/* TODO: and unload the file content */
 	}
 
 	if (error || !patch_ptr)
@@ -640,8 +628,6 @@ int git_patch_from_diff(
 	else
 		*patch_ptr = patch;
 
-	if (error == GIT_EUSER)
-		giterr_clear(); /* don't leave error message set invalidly */
 	return error;
 }
 
@@ -905,7 +891,7 @@ static int diff_patch_line_cb(
 	GIT_UNUSED(hunk_);
 
 	hunk = git_array_last(patch->hunks);
-	GITERR_CHECK_ALLOC(hunk);
+	assert(hunk); /* programmer error if no hunk is available */
 
 	line = git_array_alloc(patch->lines);
 	GITERR_CHECK_ALLOC(line);
diff --git a/src/diff_print.c b/src/diff_print.c
index b04b11515..7a70e2b18 100644
--- a/src/diff_print.c
+++ b/src/diff_print.c
@@ -89,12 +89,6 @@ char git_diff_status_char(git_delta_t status)
 	return code;
 }
 
-static int callback_error(void)
-{
-	giterr_clear();
-	return GIT_EUSER;
-}
-
 static int diff_print_one_name_only(
 	const git_diff_delta *delta, float progress, void *data)
 {
@@ -108,19 +102,16 @@ static int diff_print_one_name_only(
 		return 0;
 
 	git_buf_clear(out);
-
-	if (git_buf_puts(out, delta->new_file.path) < 0 ||
-		git_buf_putc(out, '\n'))
+	git_buf_puts(out, delta->new_file.path);
+	git_buf_putc(out, '\n');
+	if (git_buf_oom(out))
 		return -1;
 
 	pi->line.origin      = GIT_DIFF_LINE_FILE_HDR;
 	pi->line.content     = git_buf_cstr(out);
 	pi->line.content_len = git_buf_len(out);
 
-	if (pi->print_cb(delta, NULL, &pi->line, pi->payload))
-		return callback_error();
-
-	return 0;
+	return pi->print_cb(delta, NULL, &pi->line, pi->payload);
 }
 
 static int diff_print_one_name_status(
@@ -154,7 +145,6 @@ static int diff_print_one_name_status(
 		git_buf_printf(out, "%c\t%s%c\n", code, delta->old_file.path, old_suffix);
 	else
 		git_buf_printf(out, "%c\t%s\n", code, delta->old_file.path);
-
 	if (git_buf_oom(out))
 		return -1;
 
@@ -162,10 +152,7 @@ static int diff_print_one_name_status(
 	pi->line.content     = git_buf_cstr(out);
 	pi->line.content_len = git_buf_len(out);
 
-	if (pi->print_cb(delta, NULL, &pi->line, pi->payload))
-		return callback_error();
-
-	return 0;
+	return pi->print_cb(delta, NULL, &pi->line, pi->payload);
 }
 
 static int diff_print_one_raw(
@@ -208,10 +195,7 @@ static int diff_print_one_raw(
 	pi->line.content     = git_buf_cstr(out);
 	pi->line.content_len = git_buf_len(out);
 
-	if (pi->print_cb(delta, NULL, &pi->line, pi->payload))
-		return callback_error();
-
-	return 0;
+	return pi->print_cb(delta, NULL, &pi->line, pi->payload);
 }
 
 static int diff_print_oid_range(
@@ -238,10 +222,7 @@ static int diff_print_oid_range(
 		git_buf_printf(out, "index %s..%s\n", start_oid, end_oid);
 	}
 
-	if (git_buf_oom(out))
-		return -1;
-
-	return 0;
+	return git_buf_oom(out) ? -1 : 0;
 }
 
 static int diff_delta_format_with_paths(
@@ -285,8 +266,7 @@ int git_diff_delta__format_file_header(
 	git_buf_printf(out, "diff --git %s%s %s%s\n",
 		oldpfx, delta->old_file.path, newpfx, delta->new_file.path);
 
-	if (diff_print_oid_range(out, delta, oid_strlen) < 0)
-		return -1;
+	GITERR_CHECK_ERROR(diff_print_oid_range(out, delta, oid_strlen));
 
 	if ((delta->flags & GIT_DIFF_FLAG_BINARY) == 0)
 		diff_delta_format_with_paths(
@@ -298,6 +278,7 @@ int git_diff_delta__format_file_header(
 static int diff_print_patch_file(
 	const git_diff_delta *delta, float progress, void *data)
 {
+	int error;
 	diff_print_info *pi = data;
 	const char *oldpfx =
 		pi->diff ? pi->diff->opts.old_prefix : DIFF_OLD_PREFIX_DEFAULT;
@@ -313,36 +294,33 @@ static int diff_print_patch_file(
 		 (pi->flags & GIT_DIFF_SHOW_UNTRACKED_CONTENT) == 0))
 		return 0;
 
-	if (git_diff_delta__format_file_header(
-			pi->buf, delta, oldpfx, newpfx, pi->oid_strlen) < 0)
-		return -1;
+	if ((error = git_diff_delta__format_file_header(
+			pi->buf, delta, oldpfx, newpfx, pi->oid_strlen)) < 0)
+		return error;
 
 	pi->line.origin      = GIT_DIFF_LINE_FILE_HDR;
 	pi->line.content     = git_buf_cstr(pi->buf);
 	pi->line.content_len = git_buf_len(pi->buf);
 
-	if (pi->print_cb(delta, NULL, &pi->line, pi->payload))
-		return callback_error();
+	if ((error = pi->print_cb(delta, NULL, &pi->line, pi->payload)) != 0)
+		return error;
 
 	if ((delta->flags & GIT_DIFF_FLAG_BINARY) == 0)
 		return 0;
 
 	git_buf_clear(pi->buf);
 
-	if (diff_delta_format_with_paths(
+	if ((error = diff_delta_format_with_paths(
 			pi->buf, delta, oldpfx, newpfx,
-			"Binary files %s%s and %s%s differ\n") < 0)
-		return -1;
+			"Binary files %s%s and %s%s differ\n")) < 0)
+		return error;
 
 	pi->line.origin      = GIT_DIFF_LINE_BINARY;
 	pi->line.content     = git_buf_cstr(pi->buf);
 	pi->line.content_len = git_buf_len(pi->buf);
 	pi->line.num_lines   = 1;
 
-	if (pi->print_cb(delta, NULL, &pi->line, pi->payload))
-		return callback_error();
-
-	return 0;
+	return pi->print_cb(delta, NULL, &pi->line, pi->payload);
 }
 
 static int diff_print_patch_hunk(
@@ -359,10 +337,7 @@ static int diff_print_patch_hunk(
 	pi->line.content     = h->header;
 	pi->line.content_len = h->header_len;
 
-	if (pi->print_cb(d, h, &pi->line, pi->payload))
-		return callback_error();
-
-	return 0;
+	return pi->print_cb(d, h, &pi->line, pi->payload);
 }
 
 static int diff_print_patch_line(
@@ -376,10 +351,7 @@ static int diff_print_patch_line(
 	if (S_ISDIR(delta->new_file.mode))
 		return 0;
 
-	if (pi->print_cb(delta, hunk, line, pi->payload))
-		return callback_error();
-
-	return 0;
+	return pi->print_cb(delta, hunk, line, pi->payload);
 }
 
 /* print a git_diff to an output callback */
@@ -421,9 +393,14 @@ int git_diff_print(
 
 	if (!(error = diff_print_info_init(
 			&pi, &buf, diff, format, print_cb, payload)))
+	{
 		error = git_diff_foreach(
 			diff, print_file, print_hunk, print_line, &pi);
 
+		if (error) /* make sure error message is set */
+			giterr_set_after_callback_function(error, "git_diff_print");
+	}
+
 	git_buf_free(&buf);
 
 	return error;
@@ -444,10 +421,15 @@ int git_patch_print(
 	if (!(error = diff_print_info_init(
 			&pi, &temp, git_patch__diff(patch),
 			GIT_DIFF_FORMAT_PATCH, print_cb, payload)))
+	{
 		error = git_patch__invoke_callbacks(
 			patch, diff_print_patch_file, diff_print_patch_hunk,
 			diff_print_patch_line, &pi);
 
+		if (error) /* make sure error message is set */
+			giterr_set_after_callback_function(error, "git_patch_print");
+	}
+
 	git_buf_free(&temp);
 
 	return error;
@@ -478,15 +460,12 @@ int git_patch_to_str(
 	int error;
 	git_buf output = GIT_BUF_INIT;
 
-	error = git_patch_print(patch, diff_print_to_buffer_cb, &output);
-
-	/* GIT_EUSER means git_buf_put in print_to_buffer_cb returned -1,
-	 * meaning a memory allocation failure, so just map to -1...
-	 */
-	if (error == GIT_EUSER)
-		error = -1;
-
-	*string = git_buf_detach(&output);
+	if (!(error = git_patch_print(patch, diff_print_to_buffer_cb, &output)))
+		*string = git_buf_detach(&output);
+	else {
+		git_buf_free(&output);
+		*string = NULL;
+	}
 
 	return error;
 }
diff --git a/src/diff_tform.c b/src/diff_tform.c
index 702e43bd3..263a64d12 100644
--- a/src/diff_tform.c
+++ b/src/diff_tform.c
@@ -13,6 +13,7 @@
 #include "hashsig.h"
 #include "path.h"
 #include "fileops.h"
+#include "config.h"
 
 static git_diff_delta *diff_delta__dup(
 	const git_diff_delta *d, git_pool *pool)
@@ -208,9 +209,7 @@ int git_diff_merge(git_diff *onto, const git_diff *from)
 			git_pool_strdup_safe(&onto->pool, onto->opts.new_prefix);
 	}
 
-	git_vector_foreach(&onto_new, i, delta)
-		git__free(delta);
-	git_vector_free(&onto_new);
+	git_vector_free_deep(&onto_new);
 	git_pool_clear(&onto_pool);
 
 	return error;
@@ -281,28 +280,22 @@ static int normalize_find_opts(
 		git_repository_config__weakptr(&cfg, diff->repo) < 0)
 		return -1;
 
-	if (given) {
+	if (given)
 		memcpy(opts, given, sizeof(*opts));
-	} else {
-		GIT_INIT_STRUCTURE(opts, GIT_DIFF_FIND_OPTIONS_VERSION);
-	}
 
 	if (!given ||
 		 (given->flags & GIT_DIFF_FIND_ALL) == GIT_DIFF_FIND_BY_CONFIG)
 	{
-		const char *val = NULL;
-
-		if (git_config_get_string(&val, cfg, "diff.renames") < 0)
-			giterr_clear();
-		else if (val) {
-			int boolval;
-			if (!git__parse_bool(&boolval, val) && !boolval) {
-				/* do nothing */
-			} else if (!strcasecmp(val, "copies") || !strcasecmp(val, "copy"))
-				opts->flags |= (GIT_DIFF_FIND_RENAMES | GIT_DIFF_FIND_COPIES);
-			else
-				opts->flags |= GIT_DIFF_FIND_RENAMES;
-		}
+		const char *rule =
+			git_config__get_string_force(cfg, "diff.renames", "true");
+		int boolval;
+
+		if (!git__parse_bool(&boolval, rule) && !boolval)
+			/* don't set FIND_RENAMES if bool value is false */;
+		else if (!strcasecmp(rule, "copies") || !strcasecmp(rule, "copy"))
+			opts->flags |= GIT_DIFF_FIND_RENAMES | GIT_DIFF_FIND_COPIES;
+		else
+			opts->flags |= GIT_DIFF_FIND_RENAMES;
 	}
 
 	/* some flags imply others */
@@ -343,14 +336,11 @@ static int normalize_find_opts(
 #undef USE_DEFAULT
 
 	if (!opts->rename_limit) {
-		int32_t limit = 0;
-
-		opts->rename_limit = DEFAULT_RENAME_LIMIT;
+		opts->rename_limit = git_config__get_int_force(
+			cfg, "diff.renamelimit", DEFAULT_RENAME_LIMIT);
 
-		if (git_config_get_int32(&limit, cfg, "diff.renameLimit") < 0)
-			giterr_clear();
-		else if (limit > 0)
-			opts->rename_limit = limit;
+		if (opts->rename_limit <= 0)
+			opts->rename_limit = DEFAULT_RENAME_LIMIT;
 	}
 
 	/* assign the internal metric with whitespace flag as payload */
@@ -450,9 +440,7 @@ static int apply_splits_and_deletes(
 	return 0;
 
 on_error:
-	git_vector_foreach(&onto, i, delta)
-		git__free(delta);
-	git_vector_free(&onto);
+	git_vector_free_deep(&onto);
 
 	return -1;
 }
@@ -824,11 +812,11 @@ int git_diff_find_similar(
 	int error = 0, result;
 	uint16_t similarity;
 	git_diff_delta *src, *tgt;
-	git_diff_find_options opts;
+	git_diff_find_options opts = GIT_DIFF_FIND_OPTIONS_INIT;
 	size_t num_deltas, num_srcs = 0, num_tgts = 0;
 	size_t tried_srcs = 0, tried_tgts = 0;
 	size_t num_rewrites = 0, num_updates = 0, num_bumped = 0;
-	void **sigcache; /* cache of similarity metric file signatures */
+	void **sigcache = NULL; /* cache of similarity metric file signatures */
 	diff_find_match *tgt2src = NULL;
 	diff_find_match *src2tgt = NULL;
 	diff_find_match *tgt2src_copy = NULL;
@@ -838,15 +826,15 @@ int git_diff_find_similar(
 	if ((error = normalize_find_opts(diff, &opts, given_opts)) < 0)
 		return error;
 
-	/* No flags set; nothing to do */
-	if ((opts.flags & GIT_DIFF_FIND_ALL) == 0)
-		return 0;
-
 	num_deltas = diff->deltas.length;
 
 	/* TODO: maybe abort if deltas.length > rename_limit ??? */
 	if (!git__is_uint32(num_deltas))
-		return 0;
+		goto cleanup;
+
+	/* No flags set; nothing to do */
+	if ((opts.flags & GIT_DIFF_FIND_ALL) == 0)
+		goto cleanup;
 
 	sigcache = git__calloc(num_deltas * 2, sizeof(void *));
 	GITERR_CHECK_ALLOC(sigcache);
@@ -1121,11 +1109,13 @@ cleanup:
 	git__free(src2tgt);
 	git__free(tgt2src_copy);
 
-	for (t = 0; t < num_deltas * 2; ++t) {
-		if (sigcache[t] != NULL)
-			opts.metric->free_signature(sigcache[t], opts.metric->payload);
+	if (sigcache) {
+		for (t = 0; t < num_deltas * 2; ++t) {
+			if (sigcache[t] != NULL)
+				opts.metric->free_signature(sigcache[t], opts.metric->payload);
+		}
+		git__free(sigcache);
 	}
-	git__free(sigcache);
 
 	if (!given_opts || !given_opts->metric)
 		git__free(opts.metric);
diff --git a/src/diff_xdiff.c b/src/diff_xdiff.c
index e0bc11f7f..e5984f1c9 100644
--- a/src/diff_xdiff.c
+++ b/src/diff_xdiff.c
@@ -28,25 +28,29 @@ static int git_xdiff_parse_hunk(git_diff_hunk *hunk, const char *header)
 {
 	/* expect something of the form "@@ -%d[,%d] +%d[,%d] @@" */
 	if (*header != '@')
-		return -1;
+		goto fail;
 	if (git_xdiff_scan_int(&header, &hunk->old_start) < 0)
-		return -1;
+		goto fail;
 	if (*header == ',') {
 		if (git_xdiff_scan_int(&header, &hunk->old_lines) < 0)
-			return -1;
+			goto fail;
 	} else
 		hunk->old_lines = 1;
 	if (git_xdiff_scan_int(&header, &hunk->new_start) < 0)
-		return -1;
+		goto fail;
 	if (*header == ',') {
 		if (git_xdiff_scan_int(&header, &hunk->new_lines) < 0)
-			return -1;
+			goto fail;
 	} else
 		hunk->new_lines = 1;
 	if (hunk->old_start < 0 || hunk->new_start < 0)
-		return -1;
+		goto fail;
 
 	return 0;
+
+fail:
+	giterr_set(GITERR_INVALID, "Malformed hunk header from xdiff");
+	return -1;
 }
 
 typedef struct {
@@ -122,8 +126,9 @@ static int git_xdiff_cb(void *priv, mmbuffer_t *bufs, int len)
 		info->hunk.header[info->hunk.header_len] = '\0';
 
 		if (output->hunk_cb != NULL &&
-			output->hunk_cb(delta, &info->hunk, output->payload))
-			output->error = GIT_EUSER;
+			(output->error = output->hunk_cb(
+				delta, &info->hunk, output->payload)))
+			return output->error;
 
 		info->old_lineno = info->hunk.old_start;
 		info->new_lineno = info->hunk.new_start;
@@ -146,10 +151,9 @@ static int git_xdiff_cb(void *priv, mmbuffer_t *bufs, int len)
 		output->error = diff_update_lines(
 			info, &line, bufs[1].ptr, bufs[1].size);
 
-		if (!output->error &&
-			output->data_cb != NULL &&
-			output->data_cb(delta, &info->hunk, &line, output->payload))
-			output->error = GIT_EUSER;
+		if (!output->error && output->data_cb != NULL)
+			output->error = output->data_cb(
+				delta, &info->hunk, &line, output->payload);
 	}
 
 	if (len == 3 && !output->error) {
@@ -168,10 +172,9 @@ static int git_xdiff_cb(void *priv, mmbuffer_t *bufs, int len)
 		output->error = diff_update_lines(
 			info, &line, bufs[2].ptr, bufs[2].size);
 
-		if (!output->error &&
-			output->data_cb != NULL &&
-			output->data_cb(delta, &info->hunk, &line, output->payload))
-			output->error = GIT_EUSER;
+		if (!output->error && output->data_cb != NULL)
+			output->error = output->data_cb(
+				delta, &info->hunk, &line, output->payload);
 	}
 
 	return output->error;
@@ -219,11 +222,9 @@ void git_xdiff_init(git_xdiff_output *xo, const git_diff_options *opts)
 
 	xo->output.diff_cb = git_xdiff;
 
-	memset(&xo->config, 0, sizeof(xo->config));
 	xo->config.ctxlen = opts ? opts->context_lines : 3;
 	xo->config.interhunkctxlen = opts ? opts->interhunk_lines : 0;
 
-	memset(&xo->params, 0, sizeof(xo->params));
 	if (flags & GIT_DIFF_IGNORE_WHITESPACE)
 		xo->params.flags |= XDF_WHITESPACE_FLAGS;
 	if (flags & GIT_DIFF_IGNORE_WHITESPACE_CHANGE)
@@ -236,6 +237,5 @@ void git_xdiff_init(git_xdiff_output *xo, const git_diff_options *opts)
 	if (flags & GIT_DIFF_MINIMAL)
 		xo->params.flags |= XDF_NEED_MINIMAL;
 
-	memset(&xo->callback, 0, sizeof(xo->callback));
 	xo->callback.outf = git_xdiff_cb;
 }
diff --git a/src/errors.c b/src/errors.c
index d04da4ca9..a0b085923 100644
--- a/src/errors.c
+++ b/src/errors.c
@@ -23,7 +23,8 @@ static void set_error(int error_class, char *string)
 {
 	git_error *error = &GIT_GLOBAL->error_t;
 
-	git__free(error->message);
+	if (error->message != string)
+		git__free(error->message);
 
 	error->message = string;
 	error->klass = error_class;
@@ -103,8 +104,10 @@ int giterr_set_regex(const regex_t *regex, int error_code)
 
 void giterr_clear(void)
 {
-	set_error(0, NULL);
-	GIT_GLOBAL->last_error = NULL;
+	if (GIT_GLOBAL->last_error != NULL) {
+		set_error(0, NULL);
+		GIT_GLOBAL->last_error = NULL;
+	}
 
 	errno = 0;
 #ifdef GIT_WIN32
@@ -134,3 +137,39 @@ const git_error *giterr_last(void)
 {
 	return GIT_GLOBAL->last_error;
 }
+
+int giterr_capture(git_error_state *state, int error_code)
+{
+	state->error_code = error_code;
+	if (error_code)
+		giterr_detach(&state->error_msg);
+	return error_code;
+}
+
+int giterr_restore(git_error_state *state)
+{
+	if (state && state->error_code && state->error_msg.message)
+		set_error(state->error_msg.klass, state->error_msg.message);
+	else
+		giterr_clear();
+
+	return state ? state->error_code : 0;
+}
+
+int giterr_system_last(void)
+{
+#ifdef GIT_WIN32
+	return GetLastError();
+#else
+	return errno;
+#endif
+}
+
+void giterr_system_set(int code)
+{
+#ifdef GIT_WIN32
+	SetLastError(code);
+#else
+	errno = code;
+#endif
+}
diff --git a/src/fetch.c b/src/fetch.c
index 276591821..5bf2b93c1 100644
--- a/src/fetch.c
+++ b/src/fetch.c
@@ -104,7 +104,7 @@ cleanup:
 int git_fetch_negotiate(git_remote *remote)
 {
 	git_transport *t = remote->transport;
-	
+
 	if (filter_wants(remote) < 0) {
 		giterr_set(GITERR_NET, "Failed to filter the reference list for wants");
 		return -1;
@@ -128,9 +128,9 @@ int git_fetch_download_pack(git_remote *remote)
 {
 	git_transport *t = remote->transport;
 
-	if(!remote->need_pack)
+	if (!remote->need_pack)
 		return 0;
 
 	return t->download_pack(t, remote->repo, &remote->stats,
-				remote->callbacks.transfer_progress, remote->callbacks.payload);
+			remote->callbacks.transfer_progress, remote->callbacks.payload);
 }
diff --git a/src/fetchhead.c b/src/fetchhead.c
index 67089d13d..4435454ef 100644
--- a/src/fetchhead.c
+++ b/src/fetchhead.c
@@ -260,8 +260,8 @@ int git_repository_fetchhead_foreach(git_repository *repo,
 	while ((line = git__strsep(&buffer, "\n")) != NULL) {
 		++line_num;
 
-		if ((error = fetchhead_ref_parse(&oid, &is_merge, &name, &remote_url,
-			line, line_num)) < 0)
+		if ((error = fetchhead_ref_parse(
+				&oid, &is_merge, &name, &remote_url, line, line_num)) < 0)
 			goto done;
 
 		if (git_buf_len(&name) > 0)
@@ -269,8 +269,9 @@ int git_repository_fetchhead_foreach(git_repository *repo,
 		else
 			ref_name = NULL;
 
-		if ((cb(ref_name, remote_url, &oid, is_merge, payload)) != 0) {
-			error = GIT_EUSER;
+		error = cb(ref_name, remote_url, &oid, is_merge, payload);
+		if (error) {
+			giterr_set_after_callback(error);
 			goto done;
 		}
 	}
diff --git a/src/fileops.c b/src/fileops.c
index 5763b370b..a60689f3f 100644
--- a/src/fileops.c
+++ b/src/fileops.c
@@ -403,7 +403,6 @@ typedef struct {
 	const char *base;
 	size_t baselen;
 	uint32_t flags;
-	int error;
 	int depth;
 } futils__rmdir_data;
 
@@ -447,8 +446,8 @@ static int futils__rm_first_parent(git_buf *path, const char *ceiling)
 
 static int futils__rmdir_recurs_foreach(void *opaque, git_buf *path)
 {
+	int error = 0;
 	futils__rmdir_data *data = opaque;
-	int error = data->error;
 	struct stat st;
 
 	if (data->depth > FUTILS_MAX_DEPTH)
@@ -474,13 +473,14 @@ static int futils__rmdir_recurs_foreach(void *opaque, git_buf *path)
 		data->depth++;
 
 		error = git_path_direach(path, 0, futils__rmdir_recurs_foreach, data);
-		if (error < 0)
-			return (error == GIT_EUSER) ? data->error : error;
 
 		data->depth--;
 
+		if (error < 0)
+			return error;
+
 		if (data->depth == 0 && (data->flags & GIT_RMDIR_SKIP_ROOT) != 0)
-			return data->error;
+			return error;
 
 		if ((error = p_rmdir(path->ptr)) < 0) {
 			if ((data->flags & GIT_RMDIR_SKIP_NONEMPTY) != 0 &&
@@ -499,28 +499,23 @@ static int futils__rmdir_recurs_foreach(void *opaque, git_buf *path)
 	else if ((data->flags & GIT_RMDIR_SKIP_NONEMPTY) == 0)
 		error = futils__error_cannot_rmdir(path->ptr, "still present");
 
-	data->error = error;
 	return error;
 }
 
 static int futils__rmdir_empty_parent(void *opaque, git_buf *path)
 {
 	futils__rmdir_data *data = opaque;
-	int error;
+	int error = 0;
 
 	if (git_buf_len(path) <= data->baselen)
-		return GIT_ITEROVER;
-
-	error = p_rmdir(git_buf_cstr(path));
+		error = GIT_ITEROVER;
 
-	if (error) {
+	else if (p_rmdir(git_buf_cstr(path)) < 0) {
 		int en = errno;
 
 		if (en == ENOENT || en == ENOTDIR) {
-			giterr_clear();
-			error = 0;
+			/* do nothing */
 		} else if (en == ENOTEMPTY || en == EEXIST || en == EBUSY) {
-			giterr_clear();
 			error = GIT_ITEROVER;
 		} else {
 			error = git_path_set_error(errno, git_buf_cstr(path), "rmdir");
@@ -535,12 +530,13 @@ int git_futils_rmdir_r(
 {
 	int error;
 	git_buf fullpath = GIT_BUF_INIT;
-	futils__rmdir_data data = { 0 };
+	futils__rmdir_data data;
 
 	/* build path and find "root" where we should start calling mkdir */
 	if (git_path_join_unrooted(&fullpath, path, base, NULL) < 0)
 		return -1;
 
+	memset(&data, 0, sizeof(data));
 	data.base    = base ? base : "";
 	data.baselen = base ? strlen(base) : 0;
 	data.flags   = flags;
@@ -548,12 +544,13 @@ int git_futils_rmdir_r(
 	error = futils__rmdir_recurs_foreach(&data, &fullpath);
 
 	/* remove now-empty parents if requested */
-	if (!error && (flags & GIT_RMDIR_EMPTY_PARENTS) != 0) {
+	if (!error && (flags & GIT_RMDIR_EMPTY_PARENTS) != 0)
 		error = git_path_walk_up(
 			&fullpath, base, futils__rmdir_empty_parent, &data);
 
-		if (error == GIT_ITEROVER)
-			error = 0;
+	if (error == GIT_ITEROVER) {
+		giterr_clear();
+		error = 0;
 	}
 
 	git_buf_free(&fullpath);
@@ -618,6 +615,8 @@ static git_futils_dirs_guess_cb git_futils__dir_guess[GIT_FUTILS_DIR__MAX] = {
 	git_futils_guess_template_dirs,
 };
 
+static int git_futils__dirs_shutdown_set = 0;
+
 void git_futils_dirs_global_shutdown(void)
 {
 	int i;
@@ -634,8 +633,6 @@ int git_futils_dirs_global_init(void)
 	for (i = 0; !error && i < GIT_FUTILS_DIR__MAX; i++)
 		error = git_futils_dirs_get(&path, i);
 
-	git__on_shutdown(git_futils_dirs_global_shutdown);
-
 	return error;
 }
 
@@ -655,9 +652,16 @@ int git_futils_dirs_get(const git_buf **out, git_futils_dir_t which)
 
 	GITERR_CHECK_ERROR(git_futils_check_selector(which));
 
-	if (!git_buf_len(&git_futils__dirs[which]))
+	if (!git_buf_len(&git_futils__dirs[which])) {
+		/* prepare shutdown if we're going to need it */
+		if (!git_futils__dirs_shutdown_set) {
+			git__on_shutdown(git_futils_dirs_global_shutdown);
+			git_futils__dirs_shutdown_set = 1;
+		}
+
 		GITERR_CHECK_ERROR(
 			git_futils__dir_guess[which](&git_futils__dirs[which]));
+	}
 
 	*out = &git_futils__dirs[which];
 	return 0;
@@ -858,7 +862,6 @@ typedef struct {
 	uint32_t flags;
 	uint32_t mkdir_flags;
 	mode_t dirmode;
-	int error;
 } cp_r_info;
 
 #define GIT_CPDIR__MKDIR_DONE_FOR_TO_ROOT (1u << 10)
@@ -896,23 +899,21 @@ static int _cp_r_callback(void *ref, git_buf *from)
 		from->ptr[git_path_basename_offset(from)] == '.')
 		return 0;
 
-	if (git_buf_joinpath(
-			&info->to, info->to_root, from->ptr + info->from_prefix) < 0) {
-		error = -1;
-		goto exit;
-	}
+	if ((error = git_buf_joinpath(
+			&info->to, info->to_root, from->ptr + info->from_prefix)) < 0)
+		return error;
 
 	if (!(error = git_path_lstat(info->to.ptr, &to_st)))
 		exists = true;
 	else if (error != GIT_ENOTFOUND)
-		goto exit;
+		return error;
 	else {
 		giterr_clear();
 		error = 0;
 	}
 
 	if ((error = git_path_lstat(from->ptr, &from_st)) < 0)
-		goto exit;
+		return error;
 
 	if (S_ISDIR(from_st.st_mode)) {
 		mode_t oldmode = info->dirmode;
@@ -926,17 +927,13 @@ static int _cp_r_callback(void *ref, git_buf *from)
 			error = _cp_r_mkdir(info, from);
 
 		/* recurse onto target directory */
-		if (!error && (!exists || S_ISDIR(to_st.st_mode))) {
+		if (!error && (!exists || S_ISDIR(to_st.st_mode)))
 			error = git_path_direach(from, 0, _cp_r_callback, info);
 
-			if (error == GIT_EUSER)
-				error = info->error;
-		}
-
 		if (oldmode != 0)
 			info->dirmode = oldmode;
 
-		goto exit;
+		return error;
 	}
 
 	if (exists) {
@@ -946,8 +943,7 @@ static int _cp_r_callback(void *ref, git_buf *from)
 		if (p_unlink(info->to.ptr) < 0) {
 			giterr_set(GITERR_OS, "Cannot overwrite existing file '%s'",
 				info->to.ptr);
-			error = -1;
-			goto exit;
+			return GIT_EEXISTS;
 		}
 	}
 
@@ -960,7 +956,7 @@ static int _cp_r_callback(void *ref, git_buf *from)
 	/* Make container directory on demand if needed */
 	if ((info->flags & GIT_CPDIR_CREATE_EMPTY_DIRS) == 0 &&
 		(error = _cp_r_mkdir(info, from)) < 0)
-		goto exit;
+		return error;
 
 	/* make symlink or regular file */
 	if (S_ISLNK(from_st.st_mode))
@@ -974,8 +970,6 @@ static int _cp_r_callback(void *ref, git_buf *from)
 		error = git_futils_cp(from->ptr, info->to.ptr, usemode);
 	}
 
-exit:
-	info->error = error;
 	return error;
 }
 
@@ -992,11 +986,11 @@ int git_futils_cp_r(
 	if (git_buf_joinpath(&path, from, "") < 0) /* ensure trailing slash */
 		return -1;
 
+	memset(&info, 0, sizeof(info));
 	info.to_root = to;
 	info.flags   = flags;
 	info.dirmode = dirmode;
 	info.from_prefix = path.size;
-	info.error = 0;
 	git_buf_init(&info.to, 0);
 
 	/* precalculate mkdir flags */
@@ -1018,9 +1012,6 @@ int git_futils_cp_r(
 	git_buf_free(&path);
 	git_buf_free(&info.to);
 
-	if (error == GIT_EUSER)
-		error = info.error;
-
 	return error;
 }
 
diff --git a/src/filter.c b/src/filter.c
index 9f866fe88..ff81eb14e 100644
--- a/src/filter.c
+++ b/src/filter.c
@@ -69,7 +69,7 @@ static void filter_registry_shutdown(void)
 		return;
 
 	git_vector_foreach(&reg->filters, pos, fdef) {
-		if (fdef->initialized && fdef->filter && fdef->filter->shutdown) {
+		if (fdef->filter && fdef->filter->shutdown) {
 			fdef->filter->shutdown(fdef->filter);
 			fdef->initialized = false;
 		}
diff --git a/src/ignore.c b/src/ignore.c
index 27d7c7ec4..c79fe4871 100644
--- a/src/ignore.c
+++ b/src/ignore.c
@@ -74,10 +74,12 @@ static int parse_ignore_file(
 #define push_ignore_file(R,IGN,S,B,F) \
 	git_attr_cache__push_file((R),(B),(F),GIT_ATTR_FILE_FROM_FILE,parse_ignore_file,(IGN),(S))
 
-static int push_one_ignore(void *ref, git_buf *path)
+static int push_one_ignore(void *payload, git_buf *path)
 {
-	git_ignores *ign = (git_ignores *)ref;
-	return push_ignore_file(ign->repo, ign, &ign->ign_path, path->ptr, GIT_IGNORE_FILE);
+	git_ignores *ign = payload;
+
+	return push_ignore_file(
+		ign->repo, ign, &ign->ign_path, path->ptr, GIT_IGNORE_FILE);
 }
 
 static int get_internal_ignores(git_attr_file **ign, git_repository *repo)
diff --git a/src/index.c b/src/index.c
index 09e7b2346..bb81f666e 100644
--- a/src/index.c
+++ b/src/index.c
@@ -2036,11 +2036,12 @@ int git_index_read_tree(git_index *index, const git_tree *tree)
 
 	error = git_tree_walk(tree, GIT_TREEWALK_POST, read_tree_cb, &data);
 
-	git_vector_sort(&entries);
-
-	git_index_clear(index);
+	if (!error) {
+		git_vector_sort(&entries);
+		git_index_clear(index);
+		git_vector_swap(&entries, &index->entries);
+	}
 
-	git_vector_swap(&entries, &index->entries);
 	git_vector_free(&entries);
 
 	return error;
@@ -2116,8 +2117,7 @@ int git_index_add_all(
 			if (error > 0) /* return > 0 means skip this one */
 				continue;
 			if (error < 0) { /* return < 0 means abort */
-				giterr_clear();
-				error = GIT_EUSER;
+				giterr_set_after_callback(error);
 				break;
 			}
 		}
@@ -2204,11 +2204,8 @@ static int index_apply_to_all(
 				error = 0;
 				continue;
 			}
-			if (error < 0) { /* return < 0 means abort */
-				giterr_clear();
-				error = GIT_EUSER;
+			if (error < 0)   /* return < 0 means abort */
 				break;
-			}
 		}
 
 		/* index manipulation may alter entry, so don't depend on it */
@@ -2253,8 +2250,13 @@ int git_index_remove_all(
 	git_index_matched_path_cb cb,
 	void *payload)
 {
-	return index_apply_to_all(
+	int error = index_apply_to_all(
 		index, INDEX_ACTION_REMOVE, pathspec, cb, payload);
+
+	if (error) /* make sure error is set if callback stopped iteration */
+		giterr_set_after_callback(error);
+
+	return error;
 }
 
 int git_index_update_all(
@@ -2263,6 +2265,11 @@ int git_index_update_all(
 	git_index_matched_path_cb cb,
 	void *payload)
 {
-	return index_apply_to_all(
+	int error = index_apply_to_all(
 		index, INDEX_ACTION_UPDATE, pathspec, cb, payload);
+
+	if (error) /* make sure error is set if callback stopped iteration */
+		giterr_set_after_callback(error);
+
+	return error;
 }
diff --git a/src/indexer.c b/src/indexer.c
index 852a04120..6132571cc 100644
--- a/src/indexer.c
+++ b/src/indexer.c
@@ -386,12 +386,10 @@ on_error:
 
 static int do_progress_callback(git_indexer *idx, git_transfer_progress *stats)
 {
-	if (idx->progress_cb &&
-		idx->progress_cb(stats, idx->progress_payload)) {
-			giterr_clear();
-			return GIT_EUSER;
-	}
-
+	if (idx->progress_cb)
+		return giterr_set_after_callback_function(
+			idx->progress_cb(stats, idx->progress_payload),
+			"indexer progress");
 	return 0;
 }
 
@@ -443,8 +441,8 @@ int git_indexer_append(git_indexer *idx, const void *data, size_t size, git_tran
 
 	processed = stats->indexed_objects;
 
-	if (git_filebuf_write(&idx->pack_file, data, size) < 0)
-		return -1;
+	if ((error = git_filebuf_write(&idx->pack_file, data, size)) < 0)
+		return error;
 
 	hash_partially(idx, data, (int)size);
 
@@ -452,12 +450,12 @@ int git_indexer_append(git_indexer *idx, const void *data, size_t size, git_tran
 	if (idx->opened_pack) {
 		idx->pack->mwf.size += size;
 	} else {
-		if (open_pack(&idx->pack, idx->pack_file.path_lock) < 0)
-			return -1;
+		if ((error = open_pack(&idx->pack, idx->pack_file.path_lock)) < 0)
+			return error;
 		idx->opened_pack = 1;
 		mwf = &idx->pack->mwf;
-		if (git_mwindow_file_register(&idx->pack->mwf) < 0)
-			return -1;
+		if ((error = git_mwindow_file_register(&idx->pack->mwf)) < 0)
+			return error;
 	}
 
 	if (!idx->parsed_header) {
@@ -466,8 +464,8 @@ int git_indexer_append(git_indexer *idx, const void *data, size_t size, git_tran
 		if ((unsigned)idx->pack->mwf.size < sizeof(struct git_pack_header))
 			return 0;
 
-		if (parse_header(&idx->hdr, idx->pack) < 0)
-			return -1;
+		if ((error = parse_header(&idx->hdr, idx->pack)) < 0)
+			return error;
 
 		idx->parsed_header = 1;
 		idx->nr_objects = ntohl(hdr->hdr_entries);
@@ -497,7 +495,7 @@ int git_indexer_append(git_indexer *idx, const void *data, size_t size, git_tran
 		processed = stats->indexed_objects = 0;
 		stats->total_objects = total_objects;
 
-		if ((error = do_progress_callback(idx, stats)) < 0)
+		if ((error = do_progress_callback(idx, stats)) != 0)
 			return error;
 	}
 
@@ -505,6 +503,7 @@ int git_indexer_append(git_indexer *idx, const void *data, size_t size, git_tran
 
 	/* As the file grows any windows we try to use will be out of date */
 	git_mwindow_free_all(mwf);
+
 	while (processed < idx->nr_objects) {
 		git_packfile_stream *stream = &idx->stream;
 		git_off_t entry_start = idx->off;
@@ -522,7 +521,7 @@ int git_indexer_append(git_indexer *idx, const void *data, size_t size, git_tran
 				return 0;
 			}
 			if (error < 0)
-				return -1;
+				goto on_error;
 
 			git_mwindow_close(&w);
 			idx->entry_start = entry_start;
@@ -535,7 +534,7 @@ int git_indexer_append(git_indexer *idx, const void *data, size_t size, git_tran
 					return 0;
 				}
 				if (error < 0)
-					return -1;
+					goto on_error;
 
 				idx->have_delta = 1;
 			} else {
@@ -544,9 +543,10 @@ int git_indexer_append(git_indexer *idx, const void *data, size_t size, git_tran
 			}
 
 			idx->have_stream = 1;
-			if (git_packfile_stream_open(stream, idx->pack, idx->off) < 0)
-				goto on_error;
 
+			error = git_packfile_stream_open(stream, idx->pack, idx->off);
+			if (error < 0)
+				goto on_error;
 		}
 
 		if (idx->have_delta) {
@@ -580,7 +580,7 @@ int git_indexer_append(git_indexer *idx, const void *data, size_t size, git_tran
 		}
 		stats->received_objects++;
 
-		if ((error = do_progress_callback(idx, stats)) < 0)
+		if ((error = do_progress_callback(idx, stats)) != 0)
 			goto on_error;
 	}
 
@@ -860,7 +860,7 @@ int git_indexer_commit(git_indexer *idx, git_transfer_progress *stats)
 
 	/* Test for this before resolve_deltas(), as it plays with idx->off */
 	if (idx->off < idx->pack->mwf.size - 20) {
-		giterr_set(GITERR_INDEXER, "unexpected data at the end of the pack");
+		giterr_set(GITERR_INDEXER, "Unexpected data at the end of the pack");
 		return -1;
 	}
 
@@ -1007,30 +1007,20 @@ on_error:
 
 void git_indexer_free(git_indexer *idx)
 {
-	khiter_t k;
-	unsigned int i;
-	struct entry *e;
-	struct delta_info *delta;
-
 	if (idx == NULL)
 		return;
 
-	git_vector_foreach(&idx->objects, i, e)
-		git__free(e);
-	git_vector_free(&idx->objects);
+	git_vector_free_deep(&idx->objects);
 
 	if (idx->pack) {
-		for (k = kh_begin(idx->pack->idx_cache); k != kh_end(idx->pack->idx_cache); k++) {
-			if (kh_exist(idx->pack->idx_cache, k))
-				git__free(kh_value(idx->pack->idx_cache, k));
-		}
+		struct git_pack_entry *pentry;
+		kh_foreach_value(
+			idx->pack->idx_cache, pentry, { git__free(pentry); });
 
 		git_oidmap_free(idx->pack->idx_cache);
 	}
 
-	git_vector_foreach(&idx->deltas, i, delta)
-		git__free(delta);
-	git_vector_free(&idx->deltas);
+	git_vector_free_deep(&idx->deltas);
 	git_packfile_free(idx->pack);
 	git_filebuf_cleanup(&idx->pack_file);
 	git__free(idx);
diff --git a/src/iterator.c b/src/iterator.c
index 8646399ab..0e7d0db85 100644
--- a/src/iterator.c
+++ b/src/iterator.c
@@ -920,12 +920,7 @@ static fs_iterator_frame *fs_iterator__alloc_frame(fs_iterator *fi)
 
 static void fs_iterator__free_frame(fs_iterator_frame *ff)
 {
-	size_t i;
-	git_path_with_stat *path;
-
-	git_vector_foreach(&ff->entries, i, path)
-		git__free(path);
-	git_vector_free(&ff->entries);
+	git_vector_free_deep(&ff->entries);
 	git__free(ff);
 }
 
@@ -991,9 +986,8 @@ static int fs_iterator__expand_dir(fs_iterator *fi)
 		fi->base.start, fi->base.end, &ff->entries);
 
 	if (error < 0) {
-		git_error last_error = {0};
-
-		giterr_detach(&last_error);
+		git_error_state last_error = { 0 };
+		giterr_capture(&last_error, error);
 
 		/* these callbacks may clear the error message */
 		fs_iterator__free_frame(ff);
@@ -1001,12 +995,7 @@ static int fs_iterator__expand_dir(fs_iterator *fi)
 		/* next time return value we skipped to */
 		fi->base.flags &= ~GIT_ITERATOR_FIRST_ACCESS;
 
-		if (last_error.message) {
-			giterr_set_str(last_error.klass, last_error.message);
-			free(last_error.message);
-		}
-
-		return error;
+		return giterr_restore(&last_error);
 	}
 
 	if (ff->entries.length == 0) {
diff --git a/src/merge.c b/src/merge.c
index 00415cbc0..c0be37dd8 100644
--- a/src/merge.c
+++ b/src/merge.c
@@ -26,6 +26,7 @@
 #include "oid.h"
 #include "index.h"
 #include "filebuf.h"
+#include "config.h"
 
 #include "git2/types.h"
 #include "git2/repository.h"
@@ -253,7 +254,8 @@ int git_merge__bases_many(git_commit_list **out, git_revwalk *walk, git_commit_l
 	return 0;
 }
 
-int git_repository_mergehead_foreach(git_repository *repo,
+int git_repository_mergehead_foreach(
+	git_repository *repo,
 	git_repository_mergehead_foreach_cb cb,
 	void *payload)
 {
@@ -285,8 +287,8 @@ int git_repository_mergehead_foreach(git_repository *repo,
 		if ((error = git_oid_fromstr(&oid, line)) < 0)
 			goto cleanup;
 
-		if (cb(&oid, payload) != 0) {
-			error = GIT_EUSER;
+		if ((error = cb(&oid, payload)) != 0) {
+			giterr_set_after_callback(error);
 			goto cleanup;
 		}
 
@@ -1396,19 +1398,13 @@ static int merge_tree_normalize_opts(
 	}
 
 	if (!opts->target_limit) {
-		int32_t limit = 0;
-
-		opts->target_limit = GIT_MERGE_TREE_TARGET_LIMIT;
+		int limit = git_config__get_int_force(cfg, "merge.renamelimit", 0);
 
-		if (git_config_get_int32(&limit, cfg, "merge.renameLimit") < 0) {
-			giterr_clear();
-
-			if (git_config_get_int32(&limit, cfg, "diff.renameLimit") < 0)
-				giterr_clear();
-		}
+		if (!limit)
+			limit = git_config__get_int_force(cfg, "diff.renamelimit", 0);
 
-		if (limit > 0)
-			opts->target_limit = limit;
+		opts->target_limit = (limit <= 0) ?
+			GIT_MERGE_TREE_TARGET_LIMIT : (unsigned int)limit;
 	}
 
 	/* assign the internal metric with whitespace flag as payload */
@@ -2389,11 +2385,7 @@ done:
         git_index_set_caps(index_repo, index_repo_caps);
 
 	git_index_free(index_repo);
-
-	git_vector_foreach(&paths, i, path)
-		git__free(path);
-
-	git_vector_free(&paths);
+	git_vector_free_deep(&paths);
 
 	return error;
 }
diff --git a/src/notes.c b/src/notes.c
index beace1b50..795904917 100644
--- a/src/notes.c
+++ b/src/notes.c
@@ -378,20 +378,11 @@ cleanup:
 
 static int note_get_default_ref(const char **out, git_repository *repo)
 {
-	int ret;
 	git_config *cfg;
+	int ret = git_repository_config__weakptr(&cfg, repo);
 
-	*out = NULL;
-
-	if (git_repository_config__weakptr(&cfg, repo) < 0)
-		return -1;
-
-	ret = git_config_get_string(out, cfg, "core.notesRef");
-	if (ret == GIT_ENOTFOUND) {
-		giterr_clear();
-		*out = GIT_NOTES_DEFAULT_REF;
-		return 0;
-	}
+	*out = (ret != 0) ? NULL : git_config__get_string_force(
+		cfg, "core.notesref", GIT_NOTES_DEFAULT_REF);
 
 	return ret;
 }
@@ -592,8 +583,8 @@ int git_note_foreach(
 		return error;
 
 	while (!(error = git_note_next(&note_id, &annotated_id, iter))) {
-		if (note_cb(&note_id, &annotated_id, payload)) {
-			error = GIT_EUSER;
+		if ((error = note_cb(&note_id, &annotated_id, payload)) != 0) {
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
diff --git a/src/odb_loose.c b/src/odb_loose.c
index ced272b33..fd4ffff1e 100644
--- a/src/odb_loose.c
+++ b/src/odb_loose.c
@@ -547,8 +547,7 @@ static int locate_object_short_oid(
 	/* Explore directory to find a unique object matching short_oid */
 	error = git_path_direach(
 		object_location, 0, fn_locate_object_short_oid, &state);
-
-	if (error && error != GIT_EUSER)
+	if (error < 0 && error != GIT_EAMBIGUOUS)
 		return error;
 
 	if (!state.found)
@@ -696,7 +695,6 @@ struct foreach_state {
 	size_t dir_len;
 	git_odb_foreach_cb cb;
 	void *data;
-	int cb_error;
 };
 
 GIT_INLINE(int) filename_to_oid(git_oid *oid, const char *ptr)
@@ -735,12 +733,8 @@ static int foreach_object_dir_cb(void *_state, git_buf *path)
 	if (filename_to_oid(&oid, path->ptr + state->dir_len) < 0)
 		return 0;
 
-	if (state->cb(&oid, state->data)) {
-		state->cb_error = GIT_EUSER;
-		return -1;
-	}
-
-	return 0;
+	return giterr_set_after_callback_function(
+		state->cb(&oid, state->data), "git_odb_foreach");
 }
 
 static int foreach_cb(void *_state, git_buf *path)
@@ -764,6 +758,8 @@ static int loose_backend__foreach(git_odb_backend *_backend, git_odb_foreach_cb
 
 	git_buf_sets(&buf, objects_dir);
 	git_path_to_dir(&buf);
+	if (git_buf_oom(&buf))
+		return -1;
 
 	memset(&state, 0, sizeof(state));
 	state.cb = cb;
@@ -774,7 +770,7 @@ static int loose_backend__foreach(git_odb_backend *_backend, git_odb_foreach_cb
 
 	git_buf_free(&buf);
 
-	return state.cb_error ? state.cb_error : error;
+	return error;
 }
 
 static int loose_backend__stream_fwrite(git_odb_stream *_stream, const git_oid *oid)
diff --git a/src/odb_pack.c b/src/odb_pack.c
index fd2ca0fd8..903b00d26 100644
--- a/src/odb_pack.c
+++ b/src/odb_pack.c
@@ -190,31 +190,39 @@ static int packfile_sort__cb(const void *a_, const void *b_)
 }
 
 
-
-static int packfile_load__cb(void *_data, git_buf *path)
+static int packfile_load__cb(void *data, git_buf *path)
 {
-	struct pack_backend *backend = (struct pack_backend *)_data;
+	struct pack_backend *backend = data;
 	struct git_pack_file *pack;
+	const char *path_str = git_buf_cstr(path);
+	size_t i, cmp_len = git_buf_len(path);
 	int error;
-	size_t i;
 
-	if (git__suffixcmp(path->ptr, ".idx") != 0)
+	if (cmp_len <= strlen(".idx") || git__suffixcmp(path_str, ".idx") != 0)
 		return 0; /* not an index */
 
+	cmp_len -= strlen(".idx");
+
 	for (i = 0; i < backend->packs.length; ++i) {
 		struct git_pack_file *p = git_vector_get(&backend->packs, i);
-		if (memcmp(p->pack_name, git_buf_cstr(path), git_buf_len(path) - strlen(".idx")) == 0)
+
+		if (memcmp(p->pack_name, path_str, cmp_len) == 0)
 			return 0;
 	}
 
 	error = git_packfile_alloc(&pack, path->ptr);
-	if (error == GIT_ENOTFOUND)
-		/* ignore missing .pack file as git does */
+
+	/* ignore missing .pack file as git does */
+	if (error == GIT_ENOTFOUND) {
+		giterr_clear();
 		return 0;
-	else if (error < 0)
-		return error;
+	}
+
+	if (!error)
+		error = git_vector_insert(&backend->packs, pack);
+
+	return error;
 
-	return git_vector_insert(&backend->packs, pack);
 }
 
 static int pack_entry_find_inner(
@@ -314,13 +322,12 @@ static int pack_entry_find_prefix(
  * Implement the git_odb_backend API calls
  *
  ***********************************************************/
-static int pack_backend__refresh(git_odb_backend *_backend)
+static int pack_backend__refresh(git_odb_backend *backend_)
 {
-	struct pack_backend *backend = (struct pack_backend *)_backend;
-
 	int error;
 	struct stat st;
 	git_buf path = GIT_BUF_INIT;
+	struct pack_backend *backend = (struct pack_backend *)backend_;
 
 	if (backend->pack_folder == NULL)
 		return 0;
@@ -334,12 +341,9 @@ static int pack_backend__refresh(git_odb_backend *_backend)
 	error = git_path_direach(&path, 0, packfile_load__cb, backend);
 
 	git_buf_free(&path);
-
-	if (error < 0)
-		return -1;
-
 	git_vector_sort(&backend->packs);
-	return 0;
+
+	return error;
 }
 
 static int pack_backend__read_header_internal(
diff --git a/src/pack-objects.c b/src/pack-objects.c
index 2d62507f2..335944c0c 100644
--- a/src/pack-objects.c
+++ b/src/pack-objects.c
@@ -205,14 +205,18 @@ int git_packbuilder_insert(git_packbuilder *pb, const git_oid *oid,
 	po = pb->object_list + pb->nr_objects;
 	memset(po, 0x0, sizeof(*po));
 
-	if (git_odb_read_header(&po->size, &po->type, pb->odb, oid) < 0)
-		return -1;
+	if ((ret = git_odb_read_header(&po->size, &po->type, pb->odb, oid)) < 0)
+		return ret;
 
 	pb->nr_objects++;
 	git_oid_cpy(&po->id, oid);
 	po->hash = name_hash(name);
 
 	pos = kh_put(oid, pb->object_ix, &po->id, &ret);
+	if (ret < 0) {
+		giterr_set_oom();
+		return ret;
+	}
 	assert(ret != 0);
 	kh_value(pb->object_ix, pos) = po;
 
@@ -220,12 +224,17 @@ int git_packbuilder_insert(git_packbuilder *pb, const git_oid *oid,
 
 	if (pb->progress_cb) {
 		double current_time = git__timer();
-		if ((current_time - pb->last_progress_report_time) >= MIN_PROGRESS_UPDATE_INTERVAL) {
+		double elapsed = current_time - pb->last_progress_report_time;
+
+		if (elapsed >= MIN_PROGRESS_UPDATE_INTERVAL) {
 			pb->last_progress_report_time = current_time;
-			if (pb->progress_cb(GIT_PACKBUILDER_ADDING_OBJECTS, pb->nr_objects, 0, pb->progress_cb_payload)) {
-				giterr_clear();
-				return GIT_EUSER;
-			}
+
+			ret = pb->progress_cb(
+				GIT_PACKBUILDER_ADDING_OBJECTS,
+				pb->nr_objects, 0, pb->progress_cb_payload);
+
+			if (ret)
+				return giterr_set_after_callback(ret);
 		}
 	}
 
@@ -323,8 +332,10 @@ static int write_object(git_buf *buf, git_packbuilder *pb, git_pobject *po)
 		git_hash_update(&pb->ctx, data, size) < 0)
 		goto on_error;
 
-	if (po->delta_data)
+	if (po->delta_data) {
 		git__free(po->delta_data);
+		po->delta_data = NULL;
+	}
 
 	git_odb_object_free(obj);
 	git_buf_free(&zbuf);
@@ -603,6 +614,15 @@ static int write_pack(git_packbuilder *pb,
 	error = cb(entry_oid.id, GIT_OID_RAWSZ, data);
 
 done:
+	/* if callback cancelled writing, we must still free delta_data */
+	for ( ; i < pb->nr_objects; ++i) {
+		po = write_order[i];
+		if (po->delta_data) {
+			git__free(po->delta_data);
+			po->delta_data = NULL;
+		}
+	}
+
 	git__free(write_order);
 	git_buf_free(&buf);
 	return error;
@@ -1284,21 +1304,22 @@ const git_oid *git_packbuilder_hash(git_packbuilder *pb)
 	return &pb->pack_oid;
 }
 
-static int cb_tree_walk(const char *root, const git_tree_entry *entry, void *payload)
+static int cb_tree_walk(
+	const char *root, const git_tree_entry *entry, void *payload)
 {
+	int error;
 	struct tree_walk_context *ctx = payload;
 
 	/* A commit inside a tree represents a submodule commit and should be skipped. */
 	if (git_tree_entry_type(entry) == GIT_OBJ_COMMIT)
 		return 0;
 
-	if (git_buf_sets(&ctx->buf, root) < 0 ||
-		git_buf_puts(&ctx->buf, git_tree_entry_name(entry)) < 0)
-		return -1;
+	if (!(error = git_buf_sets(&ctx->buf, root)) &&
+		!(error = git_buf_puts(&ctx->buf, git_tree_entry_name(entry))))
+		error = git_packbuilder_insert(
+			ctx->pb, git_tree_entry_id(entry), git_buf_cstr(&ctx->buf));
 
-	return git_packbuilder_insert(ctx->pb,
-		git_tree_entry_id(entry),
-		git_buf_cstr(&ctx->buf));
+	return error;
 }
 
 int git_packbuilder_insert_commit(git_packbuilder *pb, const git_oid *oid)
@@ -1318,22 +1339,17 @@ int git_packbuilder_insert_commit(git_packbuilder *pb, const git_oid *oid)
 
 int git_packbuilder_insert_tree(git_packbuilder *pb, const git_oid *oid)
 {
-	git_tree *tree;
+	int error;
+	git_tree *tree = NULL;
 	struct tree_walk_context context = { pb, GIT_BUF_INIT };
 
-	if (git_tree_lookup(&tree, pb->repo, oid) < 0 ||
-	    git_packbuilder_insert(pb, oid, NULL) < 0)
-		return -1;
-
-	if (git_tree_walk(tree, GIT_TREEWALK_PRE, cb_tree_walk, &context) < 0) {
-		git_tree_free(tree);
-		git_buf_free(&context.buf);
-		return -1;
-	}
+	if (!(error = git_tree_lookup(&tree, pb->repo, oid)) &&
+	    !(error = git_packbuilder_insert(pb, oid, NULL)))
+		error = git_tree_walk(tree, GIT_TREEWALK_PRE, cb_tree_walk, &context);
 
 	git_tree_free(tree);
 	git_buf_free(&context.buf);
-	return 0;
+	return error;
 }
 
 uint32_t git_packbuilder_object_count(git_packbuilder *pb)
diff --git a/src/pack.c b/src/pack.c
index 644b2d465..23fcf3530 100644
--- a/src/pack.c
+++ b/src/pack.c
@@ -1042,10 +1042,9 @@ int git_pack_foreach_entry(
 {
 	const unsigned char *index = p->index_map.data, *current;
 	uint32_t i;
+	int error = 0;
 
 	if (index == NULL) {
-		int error;
-
 		if ((error = pack_index_open(p)) < 0)
 			return error;
 
@@ -1062,7 +1061,6 @@ int git_pack_foreach_entry(
 
 	if (p->oids == NULL) {
 		git_vector offsets, oids;
-		int error;
 
 		if ((error = git_vector_init(&oids, p->num_objects, NULL)))
 			return error;
@@ -1084,15 +1082,16 @@ int git_pack_foreach_entry(
 			git_vector_foreach(&offsets, i, current)
 				git_vector_insert(&oids, (void*)&current[4]);
 		}
+
 		git_vector_free(&offsets);
-		p->oids = (git_oid **)oids.contents;
+		p->oids = (git_oid **)git_vector_detach(NULL, NULL, &oids);
 	}
 
 	for (i = 0; i < p->num_objects; i++)
-		if (cb(p->oids[i], data))
-			return GIT_EUSER;
+		if ((error = cb(p->oids[i], data)) != 0)
+			return giterr_set_after_callback(error);
 
-	return 0;
+	return error;
 }
 
 static int pack_entry_find_offset(
diff --git a/src/path.c b/src/path.c
index 750dd3ef7..feb273915 100644
--- a/src/path.c
+++ b/src/path.c
@@ -436,8 +436,12 @@ int git_path_walk_up(
 	while (scan >= stop) {
 		error = cb(data, &iter);
 		iter.ptr[scan] = oldc;
-		if (error < 0)
+
+		if (error) {
+			giterr_set_after_callback(error);
 			break;
+		}
+
 		scan = git_buf_rfind_next(&iter, '/');
 		if (scan >= 0) {
 			scan++;
@@ -528,7 +532,9 @@ bool git_path_is_empty_dir(const char *path)
 	if (!git_path_isdir(path))
 		return false;
 
-	if (!(error = git_buf_sets(&dir, path)))
+	if ((error = git_buf_sets(&dir, path)) != 0)
+		giterr_clear();
+	else
 		error = git_path_direach(&dir, 0, path_found_entry, NULL);
 
 	git_buf_free(&dir);
@@ -778,7 +784,7 @@ int git_path_iconv(git_path_iconv_t *ic, char **in, size_t *inlen)
 		return 0;
 
 	while (1) {
-		if (git_buf_grow(&ic->buf, wantlen) < 0)
+		if (git_buf_grow(&ic->buf, wantlen + 1) < 0)
 			return -1;
 
 		nfc    = ic->buf.ptr   + ic->buf.size;
@@ -867,7 +873,7 @@ int git_path_direach(
 		if ((error = git_path_iconv(&ic, &de_path, &de_len)) < 0)
 			break;
 #endif
-				
+
 		if ((error = git_buf_put(path, de_path, de_len)) < 0)
 			break;
 
@@ -875,8 +881,8 @@ int git_path_direach(
 
 		git_buf_truncate(path, wd_len); /* restore path */
 
-		if (error) {
-			error = GIT_EUSER;
+		if (error != 0) {
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
diff --git a/src/path.h b/src/path.h
index 3daafd265..f26175d15 100644
--- a/src/path.h
+++ b/src/path.h
@@ -255,9 +255,10 @@ enum {
  * @param flags Combination of GIT_PATH_DIR flags.
  * @param callback Callback for each entry. Passed the `payload` and each
  *		successive path inside the directory as a full path.  This may
- *		safely append text to the pathbuf if needed.
+ *		safely append text to the pathbuf if needed.  Return non-zero to
+ *		cancel iteration (and return value will be propagated back).
  * @param payload Passed to callback as first argument.
- * @return 0 on success, GIT_EUSER on non-zero callback, or error code
+ * @return 0 on success or error code from OS error or from callback
  */
 extern int git_path_direach(
 	git_buf *pathbuf,
@@ -288,7 +289,7 @@ extern int git_path_cmp(
  *		original input path.
  * @param callback Function to invoke on each path.  Passed the `payload`
  *		and the buffer containing the current path.  The path should not
- *		be modified in any way.
+ *		be modified in any way. Return non-zero to stop iteration.
  * @param state Passed to fn as the first ath.
  */
 extern int git_path_walk_up(
diff --git a/src/pathspec.c b/src/pathspec.c
index 1e7e65e90..bad8dacdb 100644
--- a/src/pathspec.c
+++ b/src/pathspec.c
@@ -102,15 +102,7 @@ int git_pathspec__vinit(
 /* free data from the pathspec vector */
 void git_pathspec__vfree(git_vector *vspec)
 {
-	git_attr_fnmatch *match;
-	unsigned int i;
-
-	git_vector_foreach(vspec, i, match) {
-		git__free(match);
-		vspec->contents[i] = NULL;
-	}
-
-	git_vector_free(vspec);
+	git_vector_free_deep(vspec);
 }
 
 struct pathspec_match_context {
diff --git a/src/pool.c b/src/pool.c
index d484769e9..146f118b4 100644
--- a/src/pool.c
+++ b/src/pool.c
@@ -190,19 +190,18 @@ void *git_pool_malloc(git_pool *pool, uint32_t items)
 
 char *git_pool_strndup(git_pool *pool, const char *str, size_t n)
 {
-	void *ptr = NULL;
+	char *ptr = NULL;
 
 	assert(pool && str && pool->item_size == sizeof(char));
 
-	if (n + 1 == 0) {
-		giterr_set_oom();
+	if ((uint32_t)(n + 1) < n)
 		return NULL;
-	}
 
 	if ((ptr = git_pool_malloc(pool, (uint32_t)(n + 1))) != NULL) {
 		memcpy(ptr, str, n);
-		*(((char *)ptr) + n) = '\0';
+		ptr[n] = '\0';
 	}
+
 	pool->has_string_alloc = 1;
 
 	return ptr;
diff --git a/src/posix.c b/src/posix.c
index b75109b83..525785f35 100644
--- a/src/posix.c
+++ b/src/posix.c
@@ -203,4 +203,40 @@ int p_write(git_file fd, const void *buf, size_t cnt)
 	return 0;
 }
 
+#ifdef NO_MMAP
 
+#include "map.h"
+
+int p_mmap(git_map *out, size_t len, int prot, int flags, int fd, git_off_t offset)
+{
+	GIT_MMAP_VALIDATE(out, len, prot, flags);
+
+	out->data = NULL;
+	out->len = 0;
+
+	if ((prot & GIT_PROT_WRITE) && ((flags & GIT_MAP_TYPE) == GIT_MAP_SHARED)) {
+		giterr_set(GITERR_OS, "Trying to map shared-writeable");
+		return -1;
+	}
+
+	out->data = malloc(len);
+	GITERR_CHECK_ALLOC(out->data);
+
+	if ((p_lseek(fd, offset, SEEK_SET) < 0) || ((size_t)p_read(fd, out->data, len) != len)) {
+		giterr_set(GITERR_OS, "mmap emulation failed");
+		return -1;
+	}
+
+	out->len = len;
+	return 0;
+}
+
+int p_munmap(git_map *map)
+{
+	assert(map != NULL);
+	free(map->data);
+
+	return 0;
+}
+
+#endif
diff --git a/src/push.c b/src/push.c
index 3c9d5bb35..dd77864a5 100644
--- a/src/push.c
+++ b/src/push.c
@@ -541,10 +541,7 @@ static int queue_objects(git_push *push)
 	error = 0;
 
 on_error:
-	git_vector_foreach(&commits, i, oid)
-		git__free(oid);
-
-	git_vector_free(&commits);
+	git_vector_free_deep(&commits);
 	return error;
 }
 
@@ -662,8 +659,9 @@ int git_push_status_foreach(git_push *push,
 	unsigned int i;
 
 	git_vector_foreach(&push->status, i, status) {
-		if (cb(status->ref, status->msg, data) < 0)
-			return GIT_EUSER;
+		int error = cb(status->ref, status->msg, data);
+		if (error)
+			return giterr_set_after_callback(error);
 	}
 
 	return 0;
diff --git a/src/refdb_fs.c b/src/refdb_fs.c
index 62d5c1047..df7cb9d4d 100644
--- a/src/refdb_fs.c
+++ b/src/refdb_fs.c
@@ -264,9 +264,9 @@ done:
 	return error;
 }
 
-static int _dirent_loose_load(void *data, git_buf *full_path)
+static int _dirent_loose_load(void *payload, git_buf *full_path)
 {
-	refdb_fs_backend *backend = (refdb_fs_backend *)data;
+	refdb_fs_backend *backend = payload;
 	const char *file_path;
 
 	if (git__suffixcmp(full_path->ptr, ".lock") == 0)
@@ -305,7 +305,7 @@ static int packed_loadloose(refdb_fs_backend *backend)
 
 	git_buf_free(&refs_path);
 
-	return (error == GIT_EUSER) ? -1 : error;
+	return error;
 }
 
 static int refdb_fs_backend__exists(
diff --git a/src/refs.c b/src/refs.c
index 472a79890..4f3a557c6 100644
--- a/src/refs.c
+++ b/src/refs.c
@@ -471,7 +471,7 @@ int git_reference_rename(
 	if ((error = git_refdb_rename(out, ref->db, ref->name, new_name, force)) < 0)
 		return error;
 
-	/* Update HEAD it was poiting to the reference being renamed. */
+	/* Update HEAD it was pointing to the reference being renamed */
 	if (should_head_be_updated &&
 		(error = git_repository_set_head(ref->db->repo, new_name)) < 0) {
 		giterr_set(GITERR_REFERENCE, "Failed to update HEAD after renaming reference");
@@ -513,20 +513,19 @@ int git_reference_foreach(
 	git_reference *ref;
 	int error;
 
-	if (git_reference_iterator_new(&iter, repo) < 0)
-		return -1;
+	if ((error = git_reference_iterator_new(&iter, repo)) < 0)
+		return error;
 
-	while ((error = git_reference_next(&ref, iter)) == 0) {
-		if (callback(ref, payload)) {
-			error = GIT_EUSER;
-			goto out;
+	while (!(error = git_reference_next(&ref, iter))) {
+		if ((error = callback(ref, payload)) != 0) {
+			giterr_set_after_callback(error);
+			break;
 		}
 	}
 
 	if (error == GIT_ITEROVER)
 		error = 0;
 
-out:
 	git_reference_iterator_free(iter);
 	return error;
 }
@@ -540,20 +539,19 @@ int git_reference_foreach_name(
 	const char *refname;
 	int error;
 
-	if (git_reference_iterator_new(&iter, repo) < 0)
-		return -1;
+	if ((error = git_reference_iterator_new(&iter, repo)) < 0)
+		return error;
 
-	while ((error = git_reference_next_name(&refname, iter)) == 0) {
-		if (callback(refname, payload)) {
-			error = GIT_EUSER;
-			goto out;
+	while (!(error = git_reference_next_name(&refname, iter))) {
+		if ((error = callback(refname, payload)) != 0) {
+			giterr_set_after_callback(error);
+			break;
 		}
 	}
 
 	if (error == GIT_ITEROVER)
 		error = 0;
 
-out:
 	git_reference_iterator_free(iter);
 	return error;
 }
@@ -568,20 +566,19 @@ int git_reference_foreach_glob(
 	const char *refname;
 	int error;
 
-	if (git_reference_iterator_glob_new(&iter, repo, glob) < 0)
-		return -1;
+	if ((error = git_reference_iterator_glob_new(&iter, repo, glob)) < 0)
+		return error;
 
-	while ((error = git_reference_next_name(&refname, iter)) == 0) {
-		if (callback(refname, payload)) {
-			error = GIT_EUSER;
-			goto out;
+	while (!(error = git_reference_next_name(&refname, iter))) {
+		if ((error = callback(refname, payload)) != 0) {
+			giterr_set_after_callback(error);
+			break;
 		}
 	}
 
 	if (error == GIT_ITEROVER)
 		error = 0;
 
-out:
 	git_reference_iterator_free(iter);
 	return error;
 }
@@ -624,7 +621,9 @@ void git_reference_iterator_free(git_reference_iterator *iter)
 
 static int cb__reflist_add(const char *ref, void *data)
 {
-	return git_vector_insert((git_vector *)data, git__strdup(ref));
+	char *name = git__strdup(ref);
+	GITERR_CHECK_ALLOC(name);
+	return git_vector_insert((git_vector *)data, name);
 }
 
 int git_reference_list(
@@ -647,8 +646,8 @@ int git_reference_list(
 		return -1;
 	}
 
-	array->strings = (char **)ref_list.contents;
-	array->count = ref_list.length;
+	array->strings = (char **)git_vector_detach(&array->count, NULL, &ref_list);
+
 	return 0;
 }
 
diff --git a/src/remote.c b/src/remote.c
index 3d890a5f1..294a8709d 100644
--- a/src/remote.c
+++ b/src/remote.c
@@ -45,7 +45,7 @@ static int add_refspec(git_remote *remote, const char *string, bool is_fetch)
 
 static int download_tags_value(git_remote *remote, git_config *cfg)
 {
-	const char *val;
+	const git_config_entry *ce;
 	git_buf buf = GIT_BUF_INIT;
 	int error;
 
@@ -53,16 +53,14 @@ static int download_tags_value(git_remote *remote, git_config *cfg)
 	if (git_buf_printf(&buf, "remote.%s.tagopt", remote->name) < 0)
 		return -1;
 
-	error = git_config_get_string(&val, cfg, git_buf_cstr(&buf));
+	error = git_config__lookup_entry(&ce, cfg, git_buf_cstr(&buf), false);
 	git_buf_free(&buf);
-	if (!error && !strcmp(val, "--no-tags"))
-		remote->download_tags = GIT_REMOTE_DOWNLOAD_TAGS_NONE;
-	else if (!error && !strcmp(val, "--tags"))
-		remote->download_tags = GIT_REMOTE_DOWNLOAD_TAGS_ALL;
 
-	if (error == GIT_ENOTFOUND) {
-		giterr_clear();
-		error = 0;
+	if (!error && ce && ce->value) {
+		if (!strcmp(ce->value, "--no-tags"))
+			remote->download_tags = GIT_REMOTE_DOWNLOAD_TAGS_NONE;
+		else if (!strcmp(ce->value, "--tags"))
+			remote->download_tags = GIT_REMOTE_DOWNLOAD_TAGS_ALL;
 	}
 
 	return error;
@@ -104,12 +102,7 @@ static int get_check_cert(int *out, git_repository *repo)
 	if ((error = git_repository_config__weakptr(&cfg, repo)) < 0)
 		return error;
 
-	if ((error = git_config_get_bool(out, cfg, "http.sslVerify")) == 0)
-		return 0;
-	else if (error != GIT_ENOTFOUND)
-		return error;
-
-	giterr_clear();
+	*out = git_config__get_bool_force(cfg, "http.sslverify", 1);
 	return 0;
 }
 
@@ -262,8 +255,7 @@ struct refspec_cb_data {
 
 static int refspec_cb(const git_config_entry *entry, void *payload)
 {
-	const struct refspec_cb_data *data = (struct refspec_cb_data *)payload;
-
+	struct refspec_cb_data *data = (struct refspec_cb_data *)payload;
 	return add_refspec(data->remote, entry->value, data->fetch);
 }
 
@@ -290,9 +282,6 @@ static int get_optional_config(
 		error = 0;
 	}
 
-	if (error < 0)
-		error = -1;
-
 	return error;
 }
 
@@ -303,7 +292,7 @@ int git_remote_load(git_remote **out, git_repository *repo, const char *name)
 	const char *val;
 	int error = 0;
 	git_config *config;
-	struct refspec_cb_data data;
+	struct refspec_cb_data data = { NULL };
 	bool optional_setting_found = false, found;
 
 	assert(out && repo && name);
@@ -325,17 +314,15 @@ int git_remote_load(git_remote **out, git_repository *repo, const char *name)
 	if ((error = get_check_cert(&remote->check_cert, repo)) < 0)
 		goto cleanup;
 
-	if ((git_vector_init(&remote->refs, 32, NULL) < 0) ||
-	    (git_vector_init(&remote->refspecs, 2, NULL) < 0) ||
-	    (git_vector_init(&remote->active_refspecs, 2, NULL) < 0)) {
+	if (git_vector_init(&remote->refs, 32, NULL) < 0 ||
+	    git_vector_init(&remote->refspecs, 2, NULL) < 0 ||
+	    git_vector_init(&remote->active_refspecs, 2, NULL) < 0) {
 		error = -1;
 		goto cleanup;
 	}
 
-	if (git_buf_printf(&buf, "remote.%s.url", name) < 0) {
-		error = -1;
+	if ((error = git_buf_printf(&buf, "remote.%s.url", name)) < 0)
 		goto cleanup;
-	}
 
 	if ((error = get_optional_config(&found, config, &buf, NULL, (void *)&val)) < 0)
 		goto cleanup;
@@ -370,6 +357,7 @@ int git_remote_load(git_remote **out, git_repository *repo, const char *name)
 
 	data.remote = remote;
 	data.fetch = true;
+
 	git_buf_clear(&buf);
 	git_buf_printf(&buf, "remote.%s.fetch", name);
 
@@ -493,7 +481,7 @@ int git_remote_save(const git_remote *remote)
 		}
 		if (error < 0) {
 			git_buf_free(&buf);
-			return -1;
+			return error;
 		}
 	}
 
@@ -641,7 +629,7 @@ int git_remote_connect(git_remote *remote, git_direction direction)
 	if (!remote->check_cert)
 		flags |= GIT_TRANSPORTFLAGS_NO_CHECK_CERT;
 
-	if ((error = t->connect(t, url, remote->callbacks.credentials, remote->callbacks.payload, direction, flags)) < 0)
+	if ((error = t->connect(t, url, remote->callbacks.credentials, remote->callbacks.payload, direction, flags)) != 0)
 		goto on_error;
 
 	remote->transport = t;
@@ -667,7 +655,8 @@ int git_remote_ls(const git_remote_head ***out, size_t *size, git_remote *remote
 int git_remote__get_http_proxy(git_remote *remote, bool use_ssl, char **proxy_url)
 {
 	git_config *cfg;
-	const char *val;
+	const git_config_entry *ce;
+	const char *val = NULL;
 	int error;
 
 	assert(remote);
@@ -684,44 +673,39 @@ int git_remote__get_http_proxy(git_remote *remote, bool use_ssl, char **proxy_ur
 	 * to least specific. */
 
 	/* remote.<name>.proxy config setting */
-	if (remote->name && 0 != *(remote->name)) {
+	if (remote->name && remote->name[0]) {
 		git_buf buf = GIT_BUF_INIT;
 
 		if ((error = git_buf_printf(&buf, "remote.%s.proxy", remote->name)) < 0)
 			return error;
 
-		if ((error = git_config_get_string(&val, cfg, git_buf_cstr(&buf))) == 0 &&
-			val && ('\0' != *val)) {
-			git_buf_free(&buf);
+		error = git_config__lookup_entry(&ce, cfg, git_buf_cstr(&buf), false);
+		git_buf_free(&buf);
 
-			*proxy_url = git__strdup(val);
-			GITERR_CHECK_ALLOC(*proxy_url);
-			return 0;
-		} else if (error != GIT_ENOTFOUND)
+		if (error < 0)
 			return error;
 
-		giterr_clear();
-		git_buf_free(&buf);
+		if (ce && ce->value) {
+			val = ce->value;
+			goto found;
+		}
 	}
 
 	/* http.proxy config setting */
-	if ((error = git_config_get_string(&val, cfg, "http.proxy")) == 0 &&
-		val && ('\0' != *val)) {
-		*proxy_url = git__strdup(val);
-		GITERR_CHECK_ALLOC(*proxy_url);
-		return 0;
-	} else if (error != GIT_ENOTFOUND)
+	if ((error = git_config__lookup_entry(&ce, cfg, "http.proxy", false)) < 0)
 		return error;
-
-	giterr_clear();
+	if (ce && ce->value) {
+		val = ce->value;
+		goto found;
+	}
 
 	/* HTTP_PROXY / HTTPS_PROXY environment variables */
 	val = use_ssl ? getenv("HTTPS_PROXY") : getenv("HTTP_PROXY");
 
-	if (val && ('\0' != *val)) {
+found:
+	if (val && val[0]) {
 		*proxy_url = git__strdup(val);
 		GITERR_CHECK_ALLOC(*proxy_url);
-		return 0;
 	}
 
 	return 0;
@@ -797,7 +781,7 @@ int git_remote_download(git_remote *remote)
 	git_vector_free(&refs);
 
 	if (error < 0)
-		return -1;
+		return error;
 
 	if ((error = git_fetch_negotiate(remote)) < 0)
 		return error;
@@ -810,10 +794,10 @@ int git_remote_fetch(git_remote *remote)
 	int error;
 
 	/* Connect and download everything */
-	if ((error = git_remote_connect(remote, GIT_DIRECTION_FETCH)) < 0)
+	if ((error = git_remote_connect(remote, GIT_DIRECTION_FETCH)) != 0)
 		return error;
 
-	if ((error = git_remote_download(remote)) < 0)
+	if ((error = git_remote_download(remote)) != 0)
 		return error;
 
 	/* We don't need to be connected anymore */
@@ -1041,7 +1025,6 @@ int git_remote_update_tips(git_remote *remote)
 	int error;
 	size_t i;
 
-
 	if (git_refspec__parse(&tagspec, GIT_REFSPEC_TAGS, true) < 0)
 		return -1;
 
@@ -1141,40 +1124,28 @@ static int remote_list_cb(const git_config_entry *entry, void *payload)
 
 int git_remote_list(git_strarray *remotes_list, git_repository *repo)
 {
-	git_config *cfg;
-	git_vector list;
 	int error;
+	git_config *cfg;
+	git_vector list = GIT_VECTOR_INIT;
 
-	if (git_repository_config__weakptr(&cfg, repo) < 0)
-		return -1;
+	if ((error = git_repository_config__weakptr(&cfg, repo)) < 0)
+		return error;
 
-	if (git_vector_init(&list, 4, git__strcmp_cb) < 0)
-		return -1;
+	if ((error = git_vector_init(&list, 4, git__strcmp_cb)) < 0)
+		return error;
 
 	error = git_config_foreach_match(
 		cfg, "^remote\\..*\\.(push)?url$", remote_list_cb, &list);
 
 	if (error < 0) {
-		size_t i;
-		char *elem;
-
-		git_vector_foreach(&list, i, elem) {
-			git__free(elem);
-		}
-
-		git_vector_free(&list);
-
-		/* cb error is converted to GIT_EUSER by git_config_foreach */
-		if (error == GIT_EUSER)
-			error = -1;
-
+		git_vector_free_deep(&list);
 		return error;
 	}
 
 	git_vector_uniq(&list, git__free);
 
-	remotes_list->strings = (char **)list.contents;
-	remotes_list->count = list.length;
+	remotes_list->strings =
+		(char **)git_vector_detach(&remotes_list->count, NULL, &list);
 
 	return 0;
 }
@@ -1261,8 +1232,7 @@ cleanup:
 	return error;
 }
 
-struct update_data
-{
+struct update_data {
 	git_config *config;
 	const char *old_remote_name;
 	const char *new_remote_name;
@@ -1278,9 +1248,7 @@ static int update_config_entries_cb(
 		return 0;
 
 	return git_config_set_string(
-		data->config,
-		entry->name,
-		data->new_remote_name);
+		data->config, entry->name, data->new_remote_name);
 }
 
 static int update_branch_remote_config_entry(
@@ -1288,20 +1256,17 @@ static int update_branch_remote_config_entry(
 	const char *old_name,
 	const char *new_name)
 {
-	git_config *config;
-	struct update_data data;
+	int error;
+	struct update_data data = { NULL };
 
-	if (git_repository_config__weakptr(&config, repo) < 0)
-		return -1;
+	if ((error = git_repository_config__weakptr(&data.config, repo)) < 0)
+		return error;
 
-	data.config = config;
 	data.old_remote_name = old_name;
 	data.new_remote_name = new_name;
 
 	return git_config_foreach_match(
-		config,
-		"branch\\..+\\.remote",
-		update_config_entries_cb, &data);
+		data.config, "branch\\..+\\.remote", update_config_entries_cb, &data);
 }
 
 static int rename_one_remote_reference(
@@ -1309,18 +1274,20 @@ static int rename_one_remote_reference(
 	const char *old_remote_name,
 	const char *new_remote_name)
 {
-	int error = -1;
+	int error;
 	git_buf new_name = GIT_BUF_INIT;
 
-	if (git_buf_printf(
+	error = git_buf_printf(
 		&new_name,
 		GIT_REFS_REMOTES_DIR "%s%s",
 		new_remote_name,
-		reference->name + strlen(GIT_REFS_REMOTES_DIR) + strlen(old_remote_name)) < 0)
-			return -1;
+		reference->name + strlen(GIT_REFS_REMOTES_DIR) + strlen(old_remote_name));
 
-	error = git_reference_rename(NULL, reference, git_buf_cstr(&new_name), 0);
-	git_reference_free(reference);
+	if (!error) {
+		error = git_reference_rename(
+			NULL, reference, git_buf_cstr(&new_name), 0);
+		git_reference_free(reference);
+	}
 
 	git_buf_free(&new_name);
 	return error;
@@ -1331,12 +1298,12 @@ static int rename_remote_references(
 	const char *old_name,
 	const char *new_name)
 {
-	int error = -1;
+	int error;
 	git_reference *ref;
 	git_reference_iterator *iter;
 
-	if (git_reference_iterator_new(&iter, repo) < 0)
-		return -1;
+	if ((error = git_reference_iterator_new(&iter, repo)) < 0)
+		return error;
 
 	while ((error = git_reference_next(&ref, iter)) == 0) {
 		if (git__prefixcmp(ref->name, GIT_REFS_REMOTES_DIR)) {
@@ -1344,18 +1311,13 @@ static int rename_remote_references(
 			continue;
 		}
 
-		if ((error = rename_one_remote_reference(ref, old_name, new_name)) < 0) {
-			git_reference_iterator_free(iter);
-			return error;
-		}
+		if ((error = rename_one_remote_reference(ref, old_name, new_name)) < 0)
+			break;
 	}
 
 	git_reference_iterator_free(iter);
 
-	if (error == GIT_ITEROVER)
-		return 0;
-
-	return error;
+	return (error == GIT_ITEROVER) ? 0 : error;
 }
 
 static int rename_fetch_refspecs(
@@ -1368,52 +1330,50 @@ static int rename_fetch_refspecs(
 	git_buf base = GIT_BUF_INIT, var = GIT_BUF_INIT, val = GIT_BUF_INIT;
 	const git_refspec *spec;
 	size_t i;
-	int error = -1;
+	int error = 0;
 
-	if (git_buf_printf(&base, "+refs/heads/*:refs/remotes/%s/*", remote->name) < 0)
-		goto cleanup;
+	if ((error = git_repository_config__weakptr(&config, remote->repo)) < 0)
+		return error;
+
+	if ((error = git_buf_printf(
+			&base, "+refs/heads/*:refs/remotes/%s/*", remote->name)) < 0)
+		return error;
 
 	git_vector_foreach(&remote->refspecs, i, spec) {
 		if (spec->push)
 			continue;
 
-		/* Every refspec is a problem refspec for an in-memory remote */
-		if (!remote->name) {
-			if (callback(spec->string, payload) < 0) {
-				error = GIT_EUSER;
-				goto cleanup;
-			}
-
-			continue;
-		}
+		/* Every refspec is a problem refspec for an in-memory remote, OR */
+		/* Does the dst part of the refspec follow the expected format? */
+		if (!remote->name ||
+			strcmp(git_buf_cstr(&base), spec->string)) {
 
-		/* Does the dst part of the refspec follow the extected standard format? */
-		if (strcmp(git_buf_cstr(&base), spec->string)) {
-			if (callback(spec->string, payload) < 0) {
-				error = GIT_EUSER;
-				goto cleanup;
+			if ((error = callback(spec->string, payload)) != 0) {
+				giterr_set_after_callback(error);
+				break;
 			}
 
 			continue;
 		}
 
 		/* If we do want to move it to the new section */
-		if (git_buf_printf(&val, "+refs/heads/*:refs/remotes/%s/*", new_name) < 0)
-			goto cleanup;
 
-		if (git_buf_printf(&var, "remote.%s.fetch", new_name) < 0)
-			goto cleanup;
+		git_buf_clear(&val);
+		git_buf_clear(&var);
 
-		if (git_repository_config__weakptr(&config, remote->repo) < 0)
-			goto cleanup;
+		if (git_buf_printf(
+				&val, "+refs/heads/*:refs/remotes/%s/*", new_name) < 0 ||
+			git_buf_printf(&var, "remote.%s.fetch", new_name) < 0)
+		{
+			error = -1;
+			break;
+		}
 
-		if (git_config_set_string(config, git_buf_cstr(&var), git_buf_cstr(&val)) < 0)
-			goto cleanup;
+		if ((error = git_config_set_string(
+				config, git_buf_cstr(&var), git_buf_cstr(&val))) < 0)
+			break;
 	}
 
-	error = 0;
-
-cleanup:
 	git_buf_free(&base);
 	git_buf_free(&var);
 	git_buf_free(&val);
@@ -1448,11 +1408,11 @@ int git_remote_rename(
 				new_name,
 				callback,
 				payload)) < 0)
-				return error;
+					return error;
 
 			remote->name = git__strdup(new_name);
+			GITERR_CHECK_ALLOC(remote->name);
 
-			if (!remote->name) return 0;
 			return git_remote_save(remote);
 		}
 
@@ -1479,11 +1439,13 @@ int git_remote_rename(
 			new_name,
 			callback,
 			payload)) < 0)
-			return error;
+				return error;
 	}
 
 	git__free(remote->name);
+
 	remote->name = git__strdup(new_name);
+	GITERR_CHECK_ALLOC(remote->name);
 
 	return 0;
 }
@@ -1655,9 +1617,7 @@ static int copy_refspecs(git_strarray *array, git_remote *remote, unsigned int p
 	return 0;
 
 on_error:
-	git_vector_foreach(&refspecs, i, dup)
-		git__free(dup);
-	git_vector_free(&refspecs);
+	git_vector_free_deep(&refspecs);
 
 	return -1;
 }
diff --git a/src/repository.c b/src/repository.c
index 278c0384e..94f6603aa 100644
--- a/src/repository.c
+++ b/src/repository.c
@@ -186,39 +186,37 @@ static int load_workdir(git_repository *repo, git_buf *parent_path)
 {
 	int         error;
 	git_config *config;
-	const char *worktree;
-	git_buf     worktree_buf = GIT_BUF_INIT;
+	const git_config_entry *ce;
+	git_buf     worktree = GIT_BUF_INIT;
 
 	if (repo->is_bare)
 		return 0;
 
-	if (git_repository_config__weakptr(&config, repo) < 0)
-		return -1;
+	if ((error = git_repository_config__weakptr(&config, repo)) < 0)
+		return error;
 
-	error = git_config_get_string(&worktree, config, "core.worktree");
-	if (!error && worktree != NULL) {
-		error = git_path_prettify_dir(
-			&worktree_buf, worktree, repo->path_repository);
-		if (error < 0)
+	if ((error = git_config__lookup_entry(
+			&ce, config, "core.worktree", false)) < 0)
+		return error;
+
+	if (ce && ce->value) {
+		if ((error = git_path_prettify_dir(
+				&worktree, ce->value, repo->path_repository)) < 0)
 			return error;
-		repo->workdir = git_buf_detach(&worktree_buf);
+
+		repo->workdir = git_buf_detach(&worktree);
 	}
-	else if (error != GIT_ENOTFOUND)
-		return error;
+	else if (parent_path && git_path_isdir(parent_path->ptr))
+		repo->workdir = git_buf_detach(parent_path);
 	else {
-		giterr_clear();
+		if (git_path_dirname_r(&worktree, repo->path_repository) < 0 ||
+			git_path_to_dir(&worktree) < 0)
+			return -1;
 
-		if (parent_path && git_path_isdir(parent_path->ptr))
-			repo->workdir = git_buf_detach(parent_path);
-		else {
-			git_path_dirname_r(&worktree_buf, repo->path_repository);
-			git_path_to_dir(&worktree_buf);
-			repo->workdir = git_buf_detach(&worktree_buf);
-		}
+		repo->workdir = git_buf_detach(&worktree);
 	}
 
 	GITERR_CHECK_ALLOC(repo->workdir);
-
 	return 0;
 }
 
@@ -1610,15 +1608,14 @@ static int at_least_one_cb(const char *refname, void *payload)
 {
 	GIT_UNUSED(refname);
 	GIT_UNUSED(payload);
-
-	return GIT_EUSER;
+	return GIT_PASSTHROUGH;
 }
 
 static int repo_contains_no_reference(git_repository *repo)
 {
 	int error = git_reference_foreach_name(repo, &at_least_one_cb, NULL);
 
-	if (error == GIT_EUSER)
+	if (error == GIT_PASSTHROUGH)
 		return 0;
 
 	if (!error)
diff --git a/src/revwalk.c b/src/revwalk.c
index 3dd14b419..c0a053211 100644
--- a/src/revwalk.c
+++ b/src/revwalk.c
@@ -112,12 +112,13 @@ static int process_commit_parents(git_revwalk *walk, git_commit_list_node *commi
 
 static int push_commit(git_revwalk *walk, const git_oid *oid, int uninteresting)
 {
+	int error;
 	git_object *obj;
 	git_otype type;
 	git_commit_list_node *commit;
 
-	if (git_object_lookup(&obj, walk->repo, oid, GIT_OBJ_ANY) < 0)
-		return -1;
+	if ((error = git_object_lookup(&obj, walk->repo, oid, GIT_OBJ_ANY)) < 0)
+		return error;
 
 	type = git_object_type(obj);
 	git_object_free(obj);
@@ -173,7 +174,6 @@ struct push_cb_data {
 static int push_glob_cb(const char *refname, void *data_)
 {
 	struct push_cb_data *data = (struct push_cb_data *)data_;
-
 	return push_ref(data->walk, refname, data->hide);
 }
 
@@ -191,6 +191,8 @@ static int push_glob(git_revwalk *walk, const char *glob, int hide)
 		git_buf_joinpath(&buf, GIT_REFS_DIR, glob);
 	else
 		git_buf_puts(&buf, glob);
+	if (git_buf_oom(&buf))
+		return -1;
 
 	/* If no '?', '*' or '[' exist, we append '/ *' to the glob */
 	wildcard = strcspn(glob, "?*[");
@@ -200,11 +202,8 @@ static int push_glob(git_revwalk *walk, const char *glob, int hide)
 	data.walk = walk;
 	data.hide = hide;
 
-	if (git_buf_oom(&buf))
-		error = -1;
-	else
-		error = git_reference_foreach_glob(
-			walk->repo, git_buf_cstr(&buf), push_glob_cb, &data);
+	error = git_reference_foreach_glob(
+		walk->repo, git_buf_cstr(&buf), push_glob_cb, &data);
 
 	git_buf_free(&buf);
 	return error;
diff --git a/src/stash.c b/src/stash.c
index 083c2a4cd..eae56966c 100644
--- a/src/stash.c
+++ b/src/stash.c
@@ -440,7 +440,7 @@ static int is_dirty_cb(const char *path, unsigned int status, void *payload)
 	GIT_UNUSED(status);
 	GIT_UNUSED(payload);
 
-	return 1;
+	return GIT_PASSTHROUGH;
 }
 
 static int ensure_there_are_changes_to_stash(
@@ -463,7 +463,7 @@ static int ensure_there_are_changes_to_stash(
 
 	error = git_status_foreach_ext(repo, &opts, is_dirty_cb, NULL);
 
-	if (error == GIT_EUSER)
+	if (error == GIT_PASSTHROUGH)
 		return 0;
 
 	if (!error)
@@ -582,12 +582,14 @@ int git_stash_foreach(
 	for (i = 0; i < max; i++) {
 		entry = git_reflog_entry_byindex(reflog, i);
 
-		if (callback(i,
+		error = callback(i,
 			git_reflog_entry_message(entry),
 			git_reflog_entry_id_new(entry),
-			payload)) {
-				error = GIT_EUSER;
-				break;
+			payload);
+
+		if (error) {
+			giterr_set_after_callback(error);
+			break;
 		}
 	}
 
diff --git a/src/status.c b/src/status.c
index 07fdcb5c3..7a1472d8d 100644
--- a/src/status.c
+++ b/src/status.c
@@ -314,8 +314,9 @@ int git_status_list_new(
 			goto done;
 	}
 
-	if ((error = git_diff__paired_foreach(
-			status->head2idx, status->idx2wd, status_collect, status)) < 0)
+	error = git_diff__paired_foreach(
+		status->head2idx, status->idx2wd, status_collect, status);
+	if (error < 0)
 		goto done;
 
 	if (flags & GIT_STATUS_OPT_SORT_CASE_SENSITIVELY)
@@ -360,19 +361,13 @@ const git_status_entry *git_status_byindex(git_status_list *status, size_t i)
 
 void git_status_list_free(git_status_list *status)
 {
-	git_status_entry *status_entry;
-	size_t i;
-
 	if (status == NULL)
 		return;
 
 	git_diff_free(status->head2idx);
 	git_diff_free(status->idx2wd);
 
-	git_vector_foreach(&status->paired, i, status_entry)
-		git__free(status_entry);
-
-	git_vector_free(&status->paired);
+	git_vector_free_deep(&status->paired);
 
 	git__memzero(status, sizeof(*status));
 	git__free(status);
@@ -397,9 +392,8 @@ int git_status_foreach_ext(
 			status_entry->head_to_index->old_file.path :
 			status_entry->index_to_workdir->old_file.path;
 
-		if (cb(path, status_entry->status, payload) != 0) {
-			error = GIT_EUSER;
-			giterr_clear();
+		if ((error = cb(path, status_entry->status, payload)) != 0) {
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
diff --git a/src/submodule.c b/src/submodule.c
index 586494fed..f6660a87e 100644
--- a/src/submodule.c
+++ b/src/submodule.c
@@ -168,9 +168,8 @@ int git_submodule_foreach(
 				break;
 		}
 
-		if (callback(sm, sm->name, payload)) {
-			giterr_clear();
-			error = GIT_EUSER;
+		if ((error = callback(sm, sm->name, payload)) != 0) {
+			giterr_set_after_callback(error);
 			break;
 		}
 	});
@@ -825,17 +824,14 @@ int git_submodule_reload(git_submodule *submodule)
 	assert(submodule);
 
 	/* refresh index data */
-
-	if (submodule_update_index(submodule) < 0)
-		return -1;
+	if ((error = submodule_update_index(submodule)) < 0)
+		return error;
 
 	/* refresh HEAD tree data */
-
-	if (submodule_update_head(submodule) < 0)
-		return -1;
+	if ((error = submodule_update_head(submodule)) < 0)
+		return error;
 
 	/* refresh config data */
-
 	mods = open_gitmodules(submodule->repo, false, NULL);
 	if (mods != NULL) {
 		git_buf path = GIT_BUF_INIT;
@@ -852,19 +848,17 @@ int git_submodule_reload(git_submodule *submodule)
 
 		git_buf_free(&path);
 		git_config_file_free(mods);
-	}
 
-	if (error < 0)
-		return error;
+		if (error < 0)
+			return error;
+	}
 
 	/* refresh wd data */
-
 	submodule->flags = submodule->flags &
 		~(GIT_SUBMODULE_STATUS_IN_WD | GIT_SUBMODULE_STATUS__WD_OID_VALID);
 
-	error = submodule_load_from_wd_lite(submodule, submodule->path, NULL);
-
-	return error;
+	return submodule_load_from_wd_lite(
+		submodule, submodule->path, submodule->repo);
 }
 
 static void submodule_copy_oid_maybe(
@@ -1087,15 +1081,14 @@ int git_submodule_parse_update(git_submodule_update_t *out, const char *value)
 }
 
 static int submodule_load_from_config(
-	const git_config_entry *entry, void *data)
+	const git_config_entry *entry, void *payload)
 {
-	git_repository *repo = data;
+	git_repository *repo = payload;
 	git_strmap *smcfg = repo->submodules;
 	const char *namestart, *property, *alternate = NULL;
-	const char *key = entry->name, *value = entry->value;
+	const char *key = entry->name, *value = entry->value, *path;
 	git_buf name = GIT_BUF_INIT;
 	git_submodule *sm;
-	bool is_path;
 	int error = 0;
 
 	if (git__prefixcmp(key, "submodule.") != 0)
@@ -1108,15 +1101,11 @@ static int submodule_load_from_config(
 		return 0;
 
 	property++;
-	is_path = (strcasecmp(property, "path") == 0);
+	path = !strcasecmp(property, "path") ? value : NULL;
 
-	if (git_buf_set(&name, namestart, property - namestart - 1) < 0)
-		return -1;
-
-	if (submodule_get(&sm, repo, name.ptr, is_path ? value : NULL) < 0) {
-		git_buf_free(&name);
-		return -1;
-	}
+	if ((error = git_buf_set(&name, namestart, property - namestart - 1)) < 0 ||
+		(error = submodule_get(&sm, repo, name.ptr, path)) < 0)
+		goto done;
 
 	sm->flags |= GIT_SUBMODULE_STATUS_IN_CONFIG;
 
@@ -1130,15 +1119,20 @@ static int submodule_load_from_config(
 
 	if (strcmp(sm->name, name.ptr) != 0) {
 		alternate = sm->name = git_buf_detach(&name);
-	} else if (is_path && value && strcmp(sm->path, value) != 0) {
+	} else if (path && strcmp(path, sm->path) != 0) {
 		alternate = sm->path = git__strdup(value);
-		if (!sm->path)
+		if (!sm->path) {
 			error = -1;
+			goto done;
+		}
 	}
+
 	if (alternate) {
 		void *old_sm = NULL;
 		git_strmap_insert2(smcfg, alternate, sm, old_sm, error);
 
+		if (error < 0)
+			goto done;
 		if (error >= 0)
 			GIT_REFCOUNT_INC(sm); /* inserted under a new key */
 
@@ -1149,42 +1143,44 @@ static int submodule_load_from_config(
 		}
 	}
 
-	git_buf_free(&name);
-	if (error < 0)
-		return error;
-
 	/* TODO: Look up path in index and if it is present but not a GITLINK
 	 * then this should be deleted (at least to match git's behavior)
 	 */
 
-	if (is_path)
-		return 0;
+	if (path)
+		goto done;
 
 	/* copy other properties into submodule entry */
 	if (strcasecmp(property, "url") == 0) {
 		git__free(sm->url);
 		sm->url = NULL;
 
-		if (value != NULL && (sm->url = git__strdup(value)) == NULL)
-			return -1;
+		if (value != NULL && (sm->url = git__strdup(value)) == NULL) {
+			error = -1;
+			goto done;
+		}
 	}
 	else if (strcasecmp(property, "update") == 0) {
-		if (git_submodule_parse_update(&sm->update, value) < 0)
-			return -1;
+		if ((error = git_submodule_parse_update(&sm->update, value)) < 0)
+			goto done;
 		sm->update_default = sm->update;
 	}
 	else if (strcasecmp(property, "fetchRecurseSubmodules") == 0) {
-		if (git__parse_bool(&sm->fetch_recurse, value) < 0)
-			return submodule_config_error("fetchRecurseSubmodules", value);
+		if (git__parse_bool(&sm->fetch_recurse, value) < 0) {
+			error = submodule_config_error("fetchRecurseSubmodules", value);
+			goto done;
+		}
 	}
 	else if (strcasecmp(property, "ignore") == 0) {
-		if (git_submodule_parse_ignore(&sm->ignore, value) < 0)
-			return -1;
+		if ((error = git_submodule_parse_ignore(&sm->ignore, value)) < 0)
+			goto done;
 		sm->ignore_default = sm->ignore;
 	}
 	/* ignore other unknown submodule properties */
 
-	return 0;
+done:
+	git_buf_free(&name);
+	return error;
 }
 
 static int submodule_load_from_wd_lite(
@@ -1192,8 +1188,7 @@ static int submodule_load_from_wd_lite(
 {
 	git_buf path = GIT_BUF_INIT;
 
-	GIT_UNUSED(name);
-	GIT_UNUSED(payload);
+	GIT_UNUSED(name); GIT_UNUSED(payload);
 
 	if (git_repository_is_bare(sm->repo))
 		return 0;
@@ -1208,7 +1203,6 @@ static int submodule_load_from_wd_lite(
 		sm->flags |= GIT_SUBMODULE_STATUS_IN_WD;
 
 	git_buf_free(&path);
-
 	return 0;
 }
 
@@ -1342,7 +1336,6 @@ static int load_submodule_config(git_repository *repo)
 {
 	int error;
 	git_oid gitmodules_oid;
-	git_buf path = GIT_BUF_INIT;
 	git_config_backend *mods = NULL;
 
 	if (repo->submodules)
@@ -1370,10 +1363,9 @@ static int load_submodule_config(git_repository *repo)
 
 	/* add submodule information from .gitmodules */
 
-	if ((mods = open_gitmodules(repo, false, &gitmodules_oid)) != NULL)
-		error = git_config_file_foreach(mods, submodule_load_from_config, repo);
-
-	if (error != 0)
+	if ((mods = open_gitmodules(repo, false, &gitmodules_oid)) != NULL &&
+		(error = git_config_file_foreach(
+			mods, submodule_load_from_config, repo)) < 0)
 		goto cleanup;
 
 	/* shallow scan submodules in work tree */
@@ -1382,8 +1374,6 @@ static int load_submodule_config(git_repository *repo)
 		error = git_submodule_foreach(repo, submodule_load_from_wd_lite, NULL);
 
 cleanup:
-	git_buf_free(&path);
-
 	if (mods != NULL)
 		git_config_file_free(mods);
 
@@ -1468,7 +1458,7 @@ static int submodule_update_config(
 	int error;
 	git_config *config;
 	git_buf key = GIT_BUF_INIT;
-	const char *old = NULL;
+	const git_config_entry *ce = NULL;
 
 	assert(submodule);
 
@@ -1480,14 +1470,16 @@ static int submodule_update_config(
 	if (error < 0)
 		goto cleanup;
 
-	if (git_config_get_string(&old, config, key.ptr) < 0)
-		giterr_clear();
+	if ((error = git_config__lookup_entry(&ce, config, key.ptr, false)) < 0)
+		goto cleanup;
 
-	if (!old && only_existing)
+	if (!ce && only_existing)
+		goto cleanup;
+	if (ce && !overwrite)
 		goto cleanup;
-	if (old && !overwrite)
+	if (value && ce && ce->value && !strcmp(ce->value, value))
 		goto cleanup;
-	if ((!old && !value) || (old && value && strcmp(old, value) == 0))
+	if (!value && (!ce || !ce->value))
 		goto cleanup;
 
 	if (!value)
diff --git a/src/tag.c b/src/tag.c
index 31a3c8b80..be56b05ce 100644
--- a/src/tag.c
+++ b/src/tag.c
@@ -418,16 +418,19 @@ typedef struct {
 
 static int tags_cb(const char *ref, void *data)
 {
+	int error;
 	git_oid oid;
 	tag_cb_data *d = (tag_cb_data *)data;
 
 	if (git__prefixcmp(ref, GIT_REFS_TAGS_DIR) != 0)
 		return 0; /* no tag */
 
-	if (git_reference_name_to_id(&oid, d->repo, ref) < 0)
-		return -1;
+	if (!(error = git_reference_name_to_id(&oid, d->repo, ref))) {
+		if ((error = d->cb(ref, &oid, d->cb_data)) != 0)
+			giterr_set_after_callback_function(error, "git_tag_foreach");
+	}
 
-	return d->cb(ref, &oid, d->cb_data);
+	return error;
 }
 
 int git_tag_foreach(git_repository *repo, git_tag_foreach_cb cb, void *cb_data)
@@ -455,8 +458,14 @@ static int tag_list_cb(const char *tag_name, git_oid *oid, void *data)
 	tag_filter_data *filter = (tag_filter_data *)data;
 	GIT_UNUSED(oid);
 
-	if (!*filter->pattern || p_fnmatch(filter->pattern, tag_name + GIT_REFS_TAGS_DIR_LEN, 0) == 0)
-		return git_vector_insert(filter->taglist, git__strdup(tag_name + GIT_REFS_TAGS_DIR_LEN));
+	if (!*filter->pattern ||
+		p_fnmatch(filter->pattern, tag_name + GIT_REFS_TAGS_DIR_LEN, 0) == 0)
+	{
+		char *matched = git__strdup(tag_name + GIT_REFS_TAGS_DIR_LEN);
+		GITERR_CHECK_ALLOC(matched);
+
+		return git_vector_insert(filter->taglist, matched);
+	}
 
 	return 0;
 }
@@ -469,20 +478,20 @@ int git_tag_list_match(git_strarray *tag_names, const char *pattern, git_reposit
 
 	assert(tag_names && repo && pattern);
 
-	if (git_vector_init(&taglist, 8, NULL) < 0)
-		return -1;
+	if ((error = git_vector_init(&taglist, 8, NULL)) < 0)
+		return error;
 
 	filter.taglist = &taglist;
 	filter.pattern = pattern;
 
 	error = git_tag_foreach(repo, &tag_list_cb, (void *)&filter);
-	if (error < 0) {
+
+	if (error < 0)
 		git_vector_free(&taglist);
-		return -1;
-	}
 
-	tag_names->strings = (char **)taglist.contents;
-	tag_names->count = taglist.length;
+	tag_names->strings =
+		(char **)git_vector_detach(&tag_names->count, NULL, &taglist);
+
 	return 0;
 }
 
diff --git a/src/transports/git.c b/src/transports/git.c
index 5dcd4eff7..21507c1c7 100644
--- a/src/transports/git.c
+++ b/src/transports/git.c
@@ -93,18 +93,19 @@ static int git_stream_read(
 	size_t buf_size,
 	size_t *bytes_read)
 {
+	int error;
 	git_stream *s = (git_stream *)stream;
 	gitno_buffer buf;
 
 	*bytes_read = 0;
 
-	if (!s->sent_command && send_command(s) < 0)
-		return -1;
+	if (!s->sent_command && (error = send_command(s)) < 0)
+		return error;
 
 	gitno_buffer_setup(&s->socket, &buf, buffer, buf_size);
 
-	if (gitno_recv(&buf) < 0)
-		return -1;
+	if ((error = gitno_recv(&buf)) < 0)
+		return error;
 
 	*bytes_read = buf.offset;
 
@@ -116,10 +117,11 @@ static int git_stream_write(
 	const char *buffer,
 	size_t len)
 {
+	int error;
 	git_stream *s = (git_stream *)stream;
 
-	if (!s->sent_command && send_command(s) < 0)
-		return -1;
+	if (!s->sent_command && (error = send_command(s)) < 0)
+		return error;
 
 	return gitno_send(&s->socket, buffer, len, 0);
 }
@@ -140,7 +142,7 @@ static void git_stream_free(git_smart_subtransport_stream *stream)
 	}
 
 	git__free(s->url);
-	git__free(s);	
+	git__free(s);
 }
 
 static int git_stream_alloc(
@@ -182,18 +184,21 @@ static int _git_uploadpack_ls(
 	char *host=NULL, *port=NULL, *path=NULL, *user=NULL, *pass=NULL;
 	const char *stream_url = url;
 	git_stream *s;
-	int error = -1;
+	int error;
 
 	*stream = NULL;
+
 	if (!git__prefixcmp(url, prefix_git))
 		stream_url += strlen(prefix_git);
 
-	if (git_stream_alloc(t, stream_url, cmd_uploadpack, stream) < 0)
-		return -1;
+	if ((error = git_stream_alloc(t, stream_url, cmd_uploadpack, stream)) < 0)
+		return error;
 
 	s = (git_stream *)*stream;
 
-	if (!(error = gitno_extract_url_parts(&host, &port, &path, &user, &pass, url, GIT_DEFAULT_PORT))) {
+	if (!(error = gitno_extract_url_parts(
+			&host, &port, &path, &user, &pass, url, GIT_DEFAULT_PORT))) {
+
 		if (!(error = gitno_connect(&s->socket, host, port, 0)))
 			t->current_stream = s;
 
diff --git a/src/transports/http.c b/src/transports/http.c
index ace0d97d0..c6aaeb9cf 100644
--- a/src/transports/http.c
+++ b/src/transports/http.c
@@ -382,9 +382,6 @@ static int on_body_fill_buffer(http_parser *parser, const char *str, size_t len)
 
 static void clear_parser_state(http_subtransport *t)
 {
-	unsigned i;
-	char *entry;
-
 	http_parser_init(&t->parser, HTTP_RESPONSE);
 	gitno_buffer_setup(&t->socket,
 		&t->parse_buffer,
@@ -407,10 +404,7 @@ static void clear_parser_state(http_subtransport *t)
 	git__free(t->location);
 	t->location = NULL;
 
-	git_vector_foreach(&t->www_authenticate, i, entry)
-		git__free(entry);
-
-	git_vector_free(&t->www_authenticate);
+	git_vector_free_deep(&t->www_authenticate);
 }
 
 static int write_chunk(gitno_socket *socket, const char *buffer, size_t len)
diff --git a/src/transports/local.c b/src/transports/local.c
index 4502f0202..4635d5dd3 100644
--- a/src/transports/local.c
+++ b/src/transports/local.c
@@ -43,43 +43,43 @@ typedef struct {
 static int add_ref(transport_local *t, const char *name)
 {
 	const char peeled[] = "^{}";
+	git_oid head_oid;
 	git_remote_head *head;
 	git_object *obj = NULL, *target = NULL;
 	git_buf buf = GIT_BUF_INIT;
 	int error;
 
-	head = git__calloc(1, sizeof(git_remote_head));
-	GITERR_CHECK_ALLOC(head);
-
-	head->name = git__strdup(name);
-	GITERR_CHECK_ALLOC(head->name);
-
-	error = git_reference_name_to_id(&head->oid, t->repo, name);
+	error = git_reference_name_to_id(&head_oid, t->repo, name);
 	if (error < 0) {
-		git__free(head->name);
-		git__free(head);
 		if (!strcmp(name, GIT_HEAD_FILE) && error == GIT_ENOTFOUND) {
-			/* This is actually okay.  Empty repos often have a HEAD that points to
-			 * a nonexistent "refs/heads/master". */
+			/* This is actually okay.  Empty repos often have a HEAD that
+			 * points to a nonexistent "refs/heads/master". */
 			giterr_clear();
 			return 0;
 		}
 		return error;
 	}
 
-	if (git_vector_insert(&t->refs, head) < 0)
-	{
+	head = git__calloc(1, sizeof(git_remote_head));
+	GITERR_CHECK_ALLOC(head);
+
+	head->name = git__strdup(name);
+	GITERR_CHECK_ALLOC(head->name);
+
+	git_oid_cpy(&head->oid, &head_oid);
+
+	if ((error = git_vector_insert(&t->refs, head)) < 0) {
 		git__free(head->name);
 		git__free(head);
-		return -1;
+		return error;
 	}
 
 	/* If it's not a tag, we don't need to try to peel it */
 	if (git__prefixcmp(name, GIT_REFS_TAGS_DIR))
 		return 0;
 
-	if (git_object_lookup(&obj, t->repo, &head->oid, GIT_OBJ_ANY) < 0)
-		return -1;
+	if ((error = git_object_lookup(&obj, t->repo, &head->oid, GIT_OBJ_ANY)) < 0)
+		return error;
 
 	head = NULL;
 
@@ -94,27 +94,24 @@ static int add_ref(transport_local *t, const char *name)
 	/* And if it's a tag, peel it, and add it to the list */
 	head = git__calloc(1, sizeof(git_remote_head));
 	GITERR_CHECK_ALLOC(head);
+
 	if (git_buf_join(&buf, 0, name, peeled) < 0)
 		return -1;
-
 	head->name = git_buf_detach(&buf);
 
-	if (git_tag_peel(&target, (git_tag *) obj) < 0)
-		goto on_error;
-
-	git_oid_cpy(&head->oid, git_object_id(target));
-	git_object_free(obj);
-	git_object_free(target);
-
-	if (git_vector_insert(&t->refs, head) < 0)
-		return -1;
+	if (!(error = git_tag_peel(&target, (git_tag *)obj))) {
+		git_oid_cpy(&head->oid, git_object_id(target));
 
-	return 0;
+		if ((error = git_vector_insert(&t->refs, head)) < 0) {
+			git__free(head->name);
+			git__free(head);
+		}
+	}
 
-on_error:
 	git_object_free(obj);
 	git_object_free(target);
-	return -1;
+
+	return error;
 }
 
 static int store_refs(transport_local *t)
@@ -222,7 +219,7 @@ static int local_ls(const git_remote_head ***out, size_t *size, git_transport *t
 		return -1;
 	}
 
-	*out = (const git_remote_head **) t->refs.contents;
+	*out = (const git_remote_head **)t->refs.contents;
 	*size = t->refs.length;
 
 	return 0;
@@ -250,8 +247,9 @@ static int local_negotiate_fetch(
 			git_oid_cpy(&rhead->loid, git_object_id(obj));
 		else if (error != GIT_ENOTFOUND)
 			return error;
+		else
+			giterr_clear();
 		git_object_free(obj);
-		giterr_clear();
 	}
 
 	return 0;
@@ -528,7 +526,7 @@ static int local_download_pack(
 		}
 	}
 
-	if ((error = git_odb_write_pack(&writepack, odb, progress_cb, progress_payload)) < 0)
+	if ((error = git_odb_write_pack(&writepack, odb, progress_cb, progress_payload)) != 0)
 		goto cleanup;
 
 	/* Write the data to the ODB */
@@ -539,7 +537,7 @@ static int local_download_pack(
 		data.progress_payload = progress_payload;
 		data.writepack = writepack;
 
-		if ((error = git_packbuilder_foreach(pack, foreach_cb, &data)) < 0)
+		if ((error = git_packbuilder_foreach(pack, foreach_cb, &data)) != 0)
 			goto cleanup;
 	}
 	error = writepack->commit(writepack, stats);
diff --git a/src/transports/smart.c b/src/transports/smart.c
index 5242beb65..69eaf9b78 100644
--- a/src/transports/smart.c
+++ b/src/transports/smart.c
@@ -23,13 +23,13 @@ static int git_smart__recv_cb(gitno_buffer *buf)
 
 	buf->offset += bytes_read;
 
-	if (t->packetsize_cb && !t->cancelled.val)
-		if (t->packetsize_cb(bytes_read, t->packetsize_payload)) {
+	if (t->packetsize_cb && !t->cancelled.val) {
+		error = t->packetsize_cb(bytes_read, t->packetsize_payload);
+		if (error) {
 			git_atomic_set(&t->cancelled, 1);
-
-			giterr_clear();
 			return GIT_EUSER;
 		}
+	}
 
 	return (int)(buf->offset - old_len);
 }
@@ -342,7 +342,7 @@ int git_transport_smart(git_transport **out, git_remote *owner, void *param)
 	t->parent.is_connected = git_smart__is_connected;
 	t->parent.read_flags = git_smart__read_flags;
 	t->parent.cancel = git_smart__cancel;
-	
+
 	t->owner = owner;
 	t->rpc = definition->rpc;
 
@@ -359,7 +359,7 @@ int git_transport_smart(git_transport **out, git_remote *owner, void *param)
 	if (definition->callback(&t->wrapped, &t->parent) < 0) {
 		git__free(t);
 		return -1;
-	}	
+	}
 
 	*out = (git_transport *) t;
 	return 0;
diff --git a/src/transports/smart_protocol.c b/src/transports/smart_protocol.c
index a4046ee43..dd9b5e0ed 100644
--- a/src/transports/smart_protocol.c
+++ b/src/transports/smart_protocol.c
@@ -45,7 +45,7 @@ int git_smart__store_refs(transport_smart *t, int flushes)
 			error = GIT_EBUFS;
 
 		if (error < 0 && error != GIT_EBUFS)
-			return -1;
+			return error;
 
 		if (error == GIT_EBUFS) {
 			if ((recvd = gitno_recv(buf)) < 0)
@@ -209,12 +209,13 @@ static int fetch_setup_walk(git_revwalk **out, git_repository *repo)
 	git_strarray refs;
 	unsigned int i;
 	git_reference *ref;
+	int error;
 
-	if (git_reference_list(&refs, repo) < 0)
-		return -1;
+	if ((error = git_reference_list(&refs, repo)) < 0)
+		return error;
 
-	if (git_revwalk_new(&walk, repo) < 0)
-		return -1;
+	if ((error = git_revwalk_new(&walk, repo)) < 0)
+		return error;
 
 	git_revwalk_sorting(walk, GIT_SORT_TIME);
 
@@ -223,13 +224,13 @@ static int fetch_setup_walk(git_revwalk **out, git_repository *repo)
 		if (!git__prefixcmp(refs.strings[i], GIT_REFS_TAGS_DIR))
 			continue;
 
-		if (git_reference_lookup(&ref, repo, refs.strings[i]) < 0)
+		if ((error = git_reference_lookup(&ref, repo, refs.strings[i])) < 0)
 			goto on_error;
 
 		if (git_reference_type(ref) == GIT_REF_SYMBOLIC)
 			continue;
 
-		if (git_revwalk_push(walk, git_reference_target(ref)) < 0)
+		if ((error = git_revwalk_push(walk, git_reference_target(ref))) < 0)
 			goto on_error;
 
 		git_reference_free(ref);
@@ -242,7 +243,7 @@ static int fetch_setup_walk(git_revwalk **out, git_repository *repo)
 on_error:
 	git_reference_free(ref);
 	git_strarray_free(&refs);
-	return -1;
+	return error;
 }
 
 static int wait_while_ack(gitno_buffer *buf)
@@ -503,7 +504,7 @@ int git_smart__download_pack(
 	}
 
 	if ((error = git_repository_odb__weakptr(&odb, repo)) < 0 ||
-		((error = git_odb_write_pack(&writepack, odb, progress_cb, progress_payload)) < 0))
+		((error = git_odb_write_pack(&writepack, odb, progress_cb, progress_payload)) != 0))
 		goto done;
 
 	/*
@@ -539,11 +540,9 @@ int git_smart__download_pack(
 		if (pkt->type == GIT_PKT_PROGRESS) {
 			if (t->progress_cb) {
 				git_pkt_progress *p = (git_pkt_progress *) pkt;
-				if (t->progress_cb(p->data, p->len, t->message_cb_payload)) {
-					giterr_clear();
-					error = GIT_EUSER;
+				error = t->progress_cb(p->data, p->len, t->message_cb_payload);
+				if (error)
 					goto done;
-				}
 			}
 			git__free(pkt);
 		} else if (pkt->type == GIT_PKT_DATA) {
@@ -551,7 +550,7 @@ int git_smart__download_pack(
 			error = writepack->append(writepack, p->data, p->len, stats);
 
 			git__free(pkt);
-			if (error < 0)
+			if (error != 0)
 				goto done;
 		} else if (pkt->type == GIT_PKT_FLUSH) {
 			/* A flush indicates the end of the packfile */
@@ -564,17 +563,15 @@ int git_smart__download_pack(
 	 * Trailing execution of progress_cb, if necessary...
 	 * Only the callback through the npp datastructure currently
 	 * updates the last_fired_bytes value. It is possible that
-	 * progress has already been reported with the correct 
+	 * progress has already been reported with the correct
 	 * "received_bytes" value, but until (if?) this is unified
 	 * then we will report progress again to be sure that the
 	 * correct last received_bytes value is reported.
 	 */
 	if (npp.callback && npp.stats->received_bytes > npp.last_fired_bytes) {
-		if (npp.callback(npp.stats, npp.payload) < 0) {
-			giterr_clear();
-			error = GIT_EUSER;
+		error = npp.callback(npp.stats, npp.payload);
+		if (error != 0)
 			goto done;
-		}
 	}
 
 	error = writepack->commit(writepack, stats);
diff --git a/src/transports/winhttp.c b/src/transports/winhttp.c
index 673cd0faf..e47e19cca 100644
--- a/src/transports/winhttp.c
+++ b/src/transports/winhttp.c
@@ -667,9 +667,11 @@ replay:
 			if (allowed_types &&
 				(!t->cred || 0 == (t->cred->credtype & allowed_types))) {
 
-				if (t->owner->cred_acquire_cb(&t->cred, t->owner->url, t->connection_data.user, allowed_types, 
-					t->owner->cred_acquire_payload) < 0)
-					return GIT_EUSER;
+				int error = t->owner->cred_acquire_cb(
+					&t->cred, t->owner->url, t->connection_data.user,
+					allowed_types, t->owner->cred_acquire_payload);
+				if (error < 0)
+					return error;
 
 				assert(t->cred);
 
diff --git a/src/tree.c b/src/tree.c
index bb59ff82b..4d77ff778 100644
--- a/src/tree.c
+++ b/src/tree.c
@@ -884,22 +884,22 @@ static int tree_walk(
 	git_vector_foreach(&tree->entries, i, entry) {
 		if (preorder) {
 			error = callback(path->ptr, entry, payload);
-			if (error > 0) {
+			if (error < 0) { /* negative value stops iteration */
+				giterr_set_after_callback_function(error, "git_tree_walk");
+				break;
+			}
+			if (error > 0) { /* positive value skips this entry */
 				error = 0;
 				continue;
 			}
-			if (error < 0) {
-				giterr_clear();
-				return GIT_EUSER;
-			}
 		}
 
 		if (git_tree_entry__is_tree(entry)) {
 			git_tree *subtree;
 			size_t path_len = git_buf_len(path);
 
-			if ((error = git_tree_lookup(
-				&subtree, tree->object.repo, &entry->oid)) < 0)
+			error = git_tree_lookup(&subtree, tree->object.repo, &entry->oid);
+			if (error < 0)
 				break;
 
 			/* append the next entry to the path */
@@ -907,21 +907,24 @@ static int tree_walk(
 			git_buf_putc(path, '/');
 
 			if (git_buf_oom(path))
-				return -1;
+				error = -1;
+			else
+				error = tree_walk(subtree, callback, path, payload, preorder);
 
-			error = tree_walk(subtree, callback, path, payload, preorder);
 			git_tree_free(subtree);
-
 			if (error != 0)
 				break;
 
 			git_buf_truncate(path, path_len);
 		}
 
-		if (!preorder && callback(path->ptr, entry, payload) < 0) {
-			giterr_clear();
-			error = GIT_EUSER;
-			break;
+		if (!preorder) {
+			error = callback(path->ptr, entry, payload);
+			if (error < 0) { /* negative value stops iteration */
+				giterr_set_after_callback_function(error, "git_tree_walk");
+				break;
+			}
+			error = 0;
 		}
 	}
 
diff --git a/src/unix/map.c b/src/unix/map.c
index 7de99c99d..e62ab3e76 100644
--- a/src/unix/map.c
+++ b/src/unix/map.c
@@ -6,7 +6,7 @@
  */
 #include <git2/common.h>
 
-#ifndef GIT_WIN32
+#if !defined(GIT_WIN32) && !defined(NO_MMAP)
 
 #include "map.h"
 #include <sys/mman.h>
diff --git a/src/vector.c b/src/vector.c
index 362e7b0c0..050e032a0 100644
--- a/src/vector.c
+++ b/src/vector.c
@@ -77,6 +77,20 @@ void git_vector_free(git_vector *v)
 	v->_alloc_size = 0;
 }
 
+void git_vector_free_deep(git_vector *v)
+{
+	size_t i;
+
+	assert(v);
+
+	for (i = 0; i < v->length; ++i) {
+		git__free(v->contents[i]);
+		v->contents[i] = NULL;
+	}
+
+	git_vector_free(v);
+}
+
 int git_vector_init(git_vector *v, size_t initial_size, git_vector_cmp cmp)
 {
 	assert(v);
@@ -90,6 +104,22 @@ int git_vector_init(git_vector *v, size_t initial_size, git_vector_cmp cmp)
 	return resize_vector(v, max(initial_size, MIN_ALLOCSIZE));
 }
 
+void **git_vector_detach(size_t *size, size_t *asize, git_vector *v)
+{
+	void **data = v->contents;
+
+	if (size)
+		*size = v->length;
+	if (asize)
+		*asize = v->_alloc_size;
+
+	v->_alloc_size = 0;
+	v->length   = 0;
+	v->contents = NULL;
+
+	return data;
+}
+
 int git_vector_insert(git_vector *v, void *element)
 {
 	assert(v);
diff --git a/src/vector.h b/src/vector.h
index 279f5c6ee..d318463c6 100644
--- a/src/vector.h
+++ b/src/vector.h
@@ -23,10 +23,13 @@ typedef struct git_vector {
 
 int git_vector_init(git_vector *v, size_t initial_size, git_vector_cmp cmp);
 void git_vector_free(git_vector *v);
+void git_vector_free_deep(git_vector *v); /* free each entry and self */
 void git_vector_clear(git_vector *v);
 int git_vector_dup(git_vector *v, const git_vector *src, git_vector_cmp cmp);
 void git_vector_swap(git_vector *a, git_vector *b);
 
+void **git_vector_detach(size_t *size, size_t *asize, git_vector *v);
+
 void git_vector_sort(git_vector *v);
 
 /** Linear search for matching entry using internal comparison function */
diff --git a/src/win32/map.c b/src/win32/map.c
index 44c6c4e2e..902ea3994 100644
--- a/src/win32/map.c
+++ b/src/win32/map.c
@@ -8,6 +8,7 @@
 #include "map.h"
 #include <errno.h>
 
+#ifndef NO_MMAP
 
 static DWORD get_page_size(void)
 {
@@ -112,4 +113,4 @@ int p_munmap(git_map *map)
 	return error;
 }
 
-
+#endif
diff --git a/tests/attr/repo.c b/tests/attr/repo.c
index ef2ad5ce9..f9ba585fb 100644
--- a/tests/attr/repo.c
+++ b/tests/attr/repo.c
@@ -129,6 +129,8 @@ static int count_attrs(
 	return 0;
 }
 
+#define CANCEL_VALUE 12345
+
 static int cancel_iteration(
 	const char *name,
 	const char *value,
@@ -140,7 +142,7 @@ static int cancel_iteration(
 	*((int *)payload) -= 1;
 
 	if (*((int *)payload) < 0)
-		return -1;
+		return CANCEL_VALUE;
 
 	return 0;
 }
@@ -166,7 +168,7 @@ void test_attr_repo__foreach(void)
 
 	count = 2;
 	cl_assert_equal_i(
-		GIT_EUSER, git_attr_foreach(
+		CANCEL_VALUE, git_attr_foreach(
 			g_repo, 0, "sub/subdir_test1", &cancel_iteration, &count)
 	);
 }
diff --git a/tests/checkout/tree.c b/tests/checkout/tree.c
index 66b01bc7f..d2e92f8e8 100644
--- a/tests/checkout/tree.c
+++ b/tests/checkout/tree.c
@@ -486,6 +486,84 @@ void test_checkout_tree__donot_update_deleted_file_by_default(void)
 	git_index_free(index);
 }
 
+struct checkout_cancel_at {
+	const char *filename;
+	int error;
+	int count;
+};
+
+static int checkout_cancel_cb(
+	git_checkout_notify_t why,
+	const char *path,
+	const git_diff_file *b,
+	const git_diff_file *t,
+	const git_diff_file *w,
+	void *payload)
+{
+	struct checkout_cancel_at *ca = payload;
+
+	GIT_UNUSED(why); GIT_UNUSED(b); GIT_UNUSED(t); GIT_UNUSED(w);
+
+	ca->count++;
+
+	if (!strcmp(path, ca->filename))
+		return ca->error;
+
+	return 0;
+}
+
+void test_checkout_tree__can_cancel_checkout_from_notify(void)
+{
+	struct checkout_cancel_at ca;
+	git_checkout_opts opts = GIT_CHECKOUT_OPTS_INIT;
+	git_oid oid;
+	git_object *obj = NULL;
+
+	assert_on_branch(g_repo, "master");
+
+	cl_git_pass(git_reference_name_to_id(&oid, g_repo, "refs/heads/dir"));
+	cl_git_pass(git_object_lookup(&obj, g_repo, &oid, GIT_OBJ_ANY));
+
+	ca.filename = "new.txt";
+	ca.error = -5555;
+	ca.count = 0;
+
+	opts.notify_flags = GIT_CHECKOUT_NOTIFY_UPDATED;
+	opts.notify_cb = checkout_cancel_cb;
+	opts.notify_payload = &ca;
+	opts.checkout_strategy = GIT_CHECKOUT_FORCE;
+
+	cl_assert(!git_path_exists("testrepo/new.txt"));
+
+	cl_git_fail_with(git_checkout_tree(g_repo, obj, &opts), -5555);
+
+	cl_assert(!git_path_exists("testrepo/new.txt"));
+
+	/* on case-insensitive FS = a/b.txt, branch_file.txt, new.txt */
+	/* on case-sensitive FS   = README, then above */
+
+	if (git_path_exists("testrepo/.git/CoNfIg")) /* case insensitive */
+		cl_assert_equal_i(3, ca.count);
+	else
+		cl_assert_equal_i(4, ca.count);
+
+	/* and again with a different stopping point and return code */
+	ca.filename = "README";
+	ca.error = 123;
+	ca.count = 0;
+
+	cl_git_fail_with(git_checkout_tree(g_repo, obj, &opts), 123);
+
+	cl_assert(!git_path_exists("testrepo/new.txt"));
+
+	if (git_path_exists("testrepo/.git/CoNfIg")) /* case insensitive */
+		cl_assert_equal_i(4, ca.count);
+	else
+		cl_assert_equal_i(1, ca.count);
+
+	git_object_free(obj);
+}
+
 void test_checkout_tree__can_checkout_with_last_workdir_item_missing(void)
 {
 	git_index *index = NULL;
diff --git a/tests/clone/nonetwork.c b/tests/clone/nonetwork.c
index a286e2a8f..3cd5fb7f6 100644
--- a/tests/clone/nonetwork.c
+++ b/tests/clone/nonetwork.c
@@ -22,7 +22,7 @@ void test_clone_nonetwork__initialize(void)
 	memset(&g_options, 0, sizeof(git_clone_options));
 	g_options.version = GIT_CLONE_OPTIONS_VERSION;
 	g_options.checkout_opts = dummy_opts;
-	g_options.checkout_opts.checkout_strategy = GIT_CHECKOUT_SAFE;
+	g_options.checkout_opts.checkout_strategy = GIT_CHECKOUT_SAFE_CREATE;
 	g_options.remote_callbacks = dummy_callbacks;
 }
 
@@ -151,6 +151,61 @@ void test_clone_nonetwork__can_checkout_given_branch(void)
 
 	cl_git_pass(git_repository_head(&g_ref, g_repo));
 	cl_assert_equal_s(git_reference_name(g_ref), "refs/heads/test");
+
+	cl_assert(git_path_exists("foo/readme.txt"));
+}
+
+static int clone_cancel_fetch_transfer_progress_cb(
+	const git_transfer_progress *stats, void *data)
+{
+	GIT_UNUSED(stats); GIT_UNUSED(data);
+	return -54321;
+}
+
+void test_clone_nonetwork__can_cancel_clone_in_fetch(void)
+{
+	g_options.checkout_branch = "test";
+
+	g_options.remote_callbacks.transfer_progress =
+		clone_cancel_fetch_transfer_progress_cb;
+
+	cl_git_fail_with(git_clone(
+		&g_repo, cl_git_fixture_url("testrepo.git"), "./foo", &g_options),
+		-54321);
+
+	cl_assert(!g_repo);
+	cl_assert(!git_path_exists("foo/readme.txt"));
+}
+
+static int clone_cancel_checkout_cb(
+	git_checkout_notify_t why,
+	const char *path,
+	const git_diff_file *b,
+	const git_diff_file *t,
+	const git_diff_file *w,
+	void *payload)
+{
+	const char *at_file = payload;
+	GIT_UNUSED(why); GIT_UNUSED(b); GIT_UNUSED(t); GIT_UNUSED(w);
+	if (!strcmp(path, at_file))
+		return -12345;
+	return 0;
+}
+
+void test_clone_nonetwork__can_cancel_clone_in_checkout(void)
+{
+	g_options.checkout_branch = "test";
+
+	g_options.checkout_opts.notify_flags = GIT_CHECKOUT_NOTIFY_UPDATED;
+	g_options.checkout_opts.notify_cb = clone_cancel_checkout_cb;
+	g_options.checkout_opts.notify_payload = "readme.txt";
+
+	cl_git_fail_with(git_clone(
+		&g_repo, cl_git_fixture_url("testrepo.git"), "./foo", &g_options),
+		-12345);
+
+	cl_assert(!g_repo);
+	cl_assert(!git_path_exists("foo/readme.txt"));
 }
 
 void test_clone_nonetwork__can_detached_head(void)
diff --git a/tests/config/read.c b/tests/config/read.c
index abc088d59..25672729f 100644
--- a/tests/config/read.c
+++ b/tests/config/read.c
@@ -247,7 +247,7 @@ void test_config_read__foreach(void)
 
 	count = 3;
 	cl_git_fail(ret = git_config_foreach(cfg, cfg_callback_countdown, &count));
-	cl_assert_equal_i(GIT_EUSER, ret);
+	cl_assert_equal_i(-100, ret);
 
 	git_config_free(cfg);
 }
diff --git a/tests/config/rename.c b/tests/config/rename.c
new file mode 100644
index 000000000..db07c798f
--- /dev/null
+++ b/tests/config/rename.c
@@ -0,0 +1,85 @@
+#include "clar_libgit2.h"
+#include "config.h"
+
+static git_repository *g_repo = NULL;
+static git_config *g_config = NULL;
+
+void test_config_rename__initialize(void)
+{
+    g_repo = cl_git_sandbox_init("testrepo.git");
+	cl_git_pass(git_repository_config(&g_config, g_repo));
+}
+
+void test_config_rename__cleanup(void)
+{
+	git_config_free(g_config);
+	g_config = NULL;
+
+	cl_git_sandbox_cleanup();
+	g_repo = NULL;
+}
+
+void test_config_rename__can_rename(void)
+{
+	const git_config_entry *ce;
+
+	cl_git_pass(git_config_get_entry(
+		&ce, g_config, "branch.track-local.remote"));
+	cl_assert_equal_s(".", ce->value);
+
+	cl_git_fail(git_config_get_entry(
+		&ce, g_config, "branch.local-track.remote"));
+
+	cl_git_pass(git_config_rename_section(
+		g_repo, "branch.track-local", "branch.local-track"));
+
+	cl_git_pass(git_config_get_entry(
+		&ce, g_config, "branch.local-track.remote"));
+	cl_assert_equal_s(".", ce->value);
+
+	cl_git_fail(git_config_get_entry(
+		&ce, g_config, "branch.track-local.remote"));
+}
+
+void test_config_rename__prevent_overwrite(void)
+{
+	const git_config_entry *ce;
+
+	cl_git_pass(git_config_set_string(
+		g_config, "branch.local-track.remote", "yellow"));
+
+	cl_git_pass(git_config_get_entry(
+		&ce, g_config, "branch.local-track.remote"));
+	cl_assert_equal_s("yellow", ce->value);
+
+	cl_git_pass(git_config_rename_section(
+		g_repo, "branch.track-local", "branch.local-track"));
+
+	cl_git_pass(git_config_get_entry(
+		&ce, g_config, "branch.local-track.remote"));
+	cl_assert_equal_s(".", ce->value);
+
+	/* so, we don't currently prevent overwrite... */
+	/* {
+		const git_error *err;
+		cl_assert((err = giterr_last()) != NULL);
+		cl_assert(err->message != NULL);
+	} */
+}
+
+static void assert_invalid_config_section_name(
+	git_repository *repo, const char *name)
+{
+	cl_git_fail_with(
+		git_config_rename_section(repo, "branch.remoteless", name),
+		GIT_EINVALIDSPEC);
+}
+
+void test_config_rename__require_a_valid_new_name(void)
+{
+	assert_invalid_config_section_name(g_repo, "");
+	assert_invalid_config_section_name(g_repo, "bra\nch");
+	assert_invalid_config_section_name(g_repo, "branc#");
+	assert_invalid_config_section_name(g_repo, "bra\nch.duh");
+	assert_invalid_config_section_name(g_repo, "branc#.duh");
+}
diff --git a/tests/config/validkeyname.c b/tests/config/validkeyname.c
index 33699737b..0ef4a9ae3 100644
--- a/tests/config/validkeyname.c
+++ b/tests/config/validkeyname.c
@@ -46,23 +46,3 @@ void test_config_validkeyname__accessing_requires_a_valid_name(void)
 	assert_invalid_config_key_name("dif.dir\nstat.lines");
 	assert_invalid_config_key_name("dif.dirstat.li\nes");
 }
-
-static void assert_invalid_config_section_name(git_repository *repo, const char *name)
-{
-	cl_git_fail_with(git_config_rename_section(repo, "branch.remoteless", name), GIT_EINVALIDSPEC);
-}
-
-void test_config_validkeyname__renaming_a_section_requires_a_valid_name(void)
-{
-	git_repository *repo;
-
-	cl_git_pass(git_repository_open(&repo, cl_fixture("testrepo.git")));
-
-	assert_invalid_config_section_name(repo, "");
-	assert_invalid_config_section_name(repo, "bra\nch");
-	assert_invalid_config_section_name(repo, "branc#");
-	assert_invalid_config_section_name(repo, "bra\nch.duh");
-	assert_invalid_config_section_name(repo, "branc#.duh");
-
-	git_repository_free(repo);
-}
diff --git a/tests/config/write.c b/tests/config/write.c
index 15f750dc0..922d75557 100644
--- a/tests/config/write.c
+++ b/tests/config/write.c
@@ -303,3 +303,4 @@ void test_config_write__updating_a_locked_config_file_returns_ELOCKED(void)
 
 	git_config_free(cfg);
 }
+
diff --git a/tests/core/path.c b/tests/core/path.c
index cf2d5e944..471491b87 100644
--- a/tests/core/path.c
+++ b/tests/core/path.c
@@ -350,15 +350,26 @@ void test_core_path__10_fromurl(void)
 
 typedef struct {
 	int expect_idx;
+	int cancel_after;
 	char **expect;
 } check_walkup_info;
 
+#define CANCEL_VALUE 1234
+
 static int check_one_walkup_step(void *ref, git_buf *path)
 {
 	check_walkup_info *info = (check_walkup_info *)ref;
+
+	if (!info->cancel_after) {
+		cl_assert_equal_s(info->expect[info->expect_idx], "[CANCEL]");
+		return CANCEL_VALUE;
+	}
+	info->cancel_after--;
+
 	cl_assert(info->expect[info->expect_idx] != NULL);
 	cl_assert_equal_s(info->expect[info->expect_idx], path->ptr);
 	info->expect_idx++;
+
 	return 0;
 }
 
@@ -381,6 +392,7 @@ void test_core_path__11_walkup(void)
 	check_walkup_info info;
 
 	info.expect = expect;
+	info.cancel_after = -1;
 
 	for (i = 0, j = 0; expect[i] != NULL; i++, j++) {
 
@@ -400,6 +412,42 @@ void test_core_path__11_walkup(void)
 	git_buf_free(&p);
 }
 
+void test_core_path__11a_walkup_cancel(void)
+{
+	git_buf p = GIT_BUF_INIT;
+	int cancel[] = { 3, 2, 1, 0 };
+	char *expect[] = {
+		"/a/b/c/d/e/", "/a/b/c/d/", "/a/b/c/", "[CANCEL]", NULL,
+		"/a/b/c/d/e", "/a/b/c/d/", "[CANCEL]", NULL,
+		"/a/b/c/d/e", "[CANCEL]", NULL,
+		"[CANCEL]", NULL,
+		NULL
+	};
+	char *root[] = { NULL, NULL, "/", "", NULL };
+	int i, j;
+	check_walkup_info info;
+
+	info.expect = expect;
+
+	for (i = 0, j = 0; expect[i] != NULL; i++, j++) {
+
+		git_buf_sets(&p, expect[i]);
+
+		info.cancel_after = cancel[j];
+		info.expect_idx = i;
+
+		cl_assert_equal_i(
+			CANCEL_VALUE,
+			git_path_walk_up(&p, root[j], check_one_walkup_step, &info)
+		);
+
+		/* skip to next run of expectations */
+		while (expect[i] != NULL) i++;
+	}
+
+	git_buf_free(&p);
+}
+
 void test_core_path__12_offset_to_path_root(void)
 {
 	cl_assert(git_path_root("non/rooted/path") == -1);
diff --git a/tests/core/pool.c b/tests/core/pool.c
index 3073c4a45..351d0c20f 100644
--- a/tests/core/pool.c
+++ b/tests/core/pool.c
@@ -139,7 +139,8 @@ void test_core_pool__strndup_limit(void)
 	git_pool p;
 
 	cl_git_pass(git_pool_init(&p, 1, 100));
-	cl_assert(git_pool_strndup(&p, "foo", -1) == NULL);
+	/* ensure 64 bit doesn't overflow */
+	cl_assert(git_pool_strndup(&p, "foo", (size_t)-1) == NULL);
 	git_pool_clear(&p);
 }
 
diff --git a/tests/diff/index.c b/tests/diff/index.c
index 8f4567137..21afe8da2 100644
--- a/tests/diff/index.c
+++ b/tests/diff/index.c
@@ -128,9 +128,7 @@ void test_diff_index__1(void)
 	cl_git_pass(git_diff_tree_to_index(&diff, g_repo, a, NULL, &opts));
 
 	cl_assert_equal_i(
-		GIT_EUSER,
-		git_diff_foreach(diff, diff_stop_after_2_files, NULL, NULL, &exp)
-	);
+		1, git_diff_foreach(diff, diff_stop_after_2_files, NULL, NULL, &exp) );
 
 	cl_assert_equal_i(2, exp.files);
 
diff --git a/tests/diff/notify.c b/tests/diff/notify.c
index cc33cb71c..da7390d3f 100644
--- a/tests/diff/notify.c
+++ b/tests/diff/notify.c
@@ -20,7 +20,7 @@ static int assert_called_notifications(
 {
 	bool found = false;
 	notify_expected *exp = (notify_expected*)payload;
-	notify_expected *e;;
+	notify_expected *e;
 
 	GIT_UNUSED(diff_so_far);
 
@@ -182,10 +182,12 @@ void test_diff_notify__notify_cb_can_abort_diff(void)
 	opts.pathspec.count   = 1;
 
 	pathspec = "file_deleted";
-	cl_git_fail(git_diff_index_to_workdir(&diff, g_repo, NULL, &opts));
+	cl_git_fail_with(
+		git_diff_index_to_workdir(&diff, g_repo, NULL, &opts), -42);
 
 	pathspec = "staged_changes_modified_file";
-	cl_git_fail(git_diff_index_to_workdir(&diff, g_repo, NULL, &opts));
+	cl_git_fail_with(
+		git_diff_index_to_workdir(&diff, g_repo, NULL, &opts), -42);
 }
 
 static int filter_all(
diff --git a/tests/diff/patch.c b/tests/diff/patch.c
index bd1598b21..0cef3bd3a 100644
--- a/tests/diff/patch.c
+++ b/tests/diff/patch.c
@@ -30,8 +30,6 @@ static int check_removal_cb(
 	const git_diff_line *line,
 	void *payload)
 {
-	GIT_UNUSED(payload);
-
 	switch (line->origin) {
 	case GIT_DIFF_LINE_FILE_HDR:
 		cl_assert_equal_s(EXPECTED_HEADER, line->content);
@@ -40,10 +38,12 @@ static int check_removal_cb(
 
 	case GIT_DIFF_LINE_HUNK_HDR:
 		cl_assert_equal_s(EXPECTED_HUNK, line->content);
-		/* Fall through */
+		goto check_hunk;
 
 	case GIT_DIFF_LINE_CONTEXT:
 	case GIT_DIFF_LINE_DELETION:
+		if (payload != NULL)
+			return *(int *)payload;
 		goto check_hunk;
 
 	default:
@@ -101,6 +101,39 @@ void test_diff_patch__can_properly_display_the_removal_of_a_file(void)
 	git_tree_free(one);
 }
 
+void test_diff_patch__can_cancel_diff_print(void)
+{
+	const char *one_sha = "26a125e";
+	const char *another_sha = "735b6a2";
+	git_tree *one, *another;
+	git_diff *diff;
+	int fail_with;
+
+	g_repo = cl_git_sandbox_init("status");
+
+	one = resolve_commit_oid_to_tree(g_repo, one_sha);
+	another = resolve_commit_oid_to_tree(g_repo, another_sha);
+
+	cl_git_pass(git_diff_tree_to_tree(&diff, g_repo, one, another, NULL));
+
+	fail_with = -2323;
+
+	cl_git_fail_with(git_diff_print(
+		diff, GIT_DIFF_FORMAT_PATCH, check_removal_cb, &fail_with),
+		fail_with);
+
+	fail_with = 45;
+
+	cl_git_fail_with(git_diff_print(
+		diff, GIT_DIFF_FORMAT_PATCH, check_removal_cb, &fail_with),
+		fail_with);
+
+	git_diff_free(diff);
+
+	git_tree_free(another);
+	git_tree_free(one);
+}
+
 void test_diff_patch__to_string(void)
 {
 	const char *one_sha = "26a125e";
diff --git a/tests/diff/rename.c b/tests/diff/rename.c
index ca6d076d6..93e69f479 100644
--- a/tests/diff/rename.c
+++ b/tests/diff/rename.c
@@ -111,6 +111,28 @@ void test_diff_rename__match_oid(void)
 
 	git_diff_free(diff);
 
+	cl_git_pass(git_diff_tree_to_tree(
+		&diff, g_repo, old_tree, new_tree, &diffopts));
+
+	/* git diff --find-copies-harder -M100 -B100 \
+	 *          31e47d8c1fa36d7f8d537b96158e3f024de0a9f2 \
+	 *          2bc7f351d20b53f1c72c16c4b036e491c478c49a
+	 */
+	opts.flags = GIT_DIFF_FIND_COPIES_FROM_UNMODIFIED |
+		GIT_DIFF_FIND_EXACT_MATCH_ONLY;
+	cl_git_pass(git_diff_find_similar(diff, &opts));
+
+	memset(&exp, 0, sizeof(exp));
+	cl_git_pass(git_diff_foreach(
+		diff, diff_file_cb, diff_hunk_cb, diff_line_cb, &exp));
+
+	cl_assert_equal_i(3, exp.files);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_UNMODIFIED]);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_COPIED]);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_RENAMED]);
+
+	git_diff_free(diff);
+
 	git_tree_free(old_tree);
 	git_tree_free(new_tree);
 }
diff --git a/tests/index/addall.c b/tests/index/addall.c
index 44c51279d..452733710 100644
--- a/tests/index/addall.c
+++ b/tests/index/addall.c
@@ -4,6 +4,7 @@
 #include "fileops.h"
 
 git_repository *g_repo = NULL;
+#define TEST_DIR "addall"
 
 void test_index_addall__initialize(void)
 {
@@ -13,6 +14,8 @@ void test_index_addall__cleanup(void)
 {
 	git_repository_free(g_repo);
 	g_repo = NULL;
+
+	cl_fixture_cleanup(TEST_DIR);
 }
 
 #define STATUS_INDEX_FLAGS \
@@ -132,6 +135,25 @@ static void check_stat_data(git_index *index, const char *path, bool match)
 	}
 }
 
+static void addall_create_test_repo(bool check_every_step)
+{
+	cl_git_pass(git_repository_init(&g_repo, TEST_DIR, false));
+	if (check_every_step)
+		check_status(g_repo, 0, 0, 0, 0, 0, 0, 0);
+
+	cl_git_mkfile(TEST_DIR "/file.foo", "a file");
+	if (check_every_step)
+		check_status(g_repo, 0, 0, 0, 1, 0, 0, 0);
+
+	cl_git_mkfile(TEST_DIR "/.gitignore", "*.foo\n");
+	if (check_every_step)
+		check_status(g_repo, 0, 0, 0, 1, 0, 0, 1);
+
+	cl_git_mkfile(TEST_DIR "/file.bar", "another file");
+	if (check_every_step)
+		check_status(g_repo, 0, 0, 0, 2, 0, 0, 1);
+}
+
 void test_index_addall__repo_lifecycle(void)
 {
 	int error;
@@ -139,43 +161,33 @@ void test_index_addall__repo_lifecycle(void)
 	git_strarray paths = { NULL, 0 };
 	char *strs[1];
 
-	cl_git_pass(git_repository_init(&g_repo, "addall", false));
-	check_status(g_repo, 0, 0, 0, 0, 0, 0, 0);
+	addall_create_test_repo(true);
 
 	cl_git_pass(git_repository_index(&index, g_repo));
 
-	cl_git_mkfile("addall/file.foo", "a file");
-	check_status(g_repo, 0, 0, 0, 1, 0, 0, 0);
-
-	cl_git_mkfile("addall/.gitignore", "*.foo\n");
-	check_status(g_repo, 0, 0, 0, 1, 0, 0, 1);
-
-	cl_git_mkfile("addall/file.bar", "another file");
-	check_status(g_repo, 0, 0, 0, 2, 0, 0, 1);
-
 	strs[0] = "file.*";
 	paths.strings = strs;
 	paths.count   = 1;
 
 	cl_git_pass(git_index_add_all(index, &paths, 0, NULL, NULL));
-	check_stat_data(index, "addall/file.bar", true);
+	check_stat_data(index, TEST_DIR "/file.bar", true);
 	check_status(g_repo, 1, 0, 0, 1, 0, 0, 1);
 
-	cl_git_rewritefile("addall/file.bar", "new content for file");
-	check_stat_data(index, "addall/file.bar", false);
+	cl_git_rewritefile(TEST_DIR "/file.bar", "new content for file");
+	check_stat_data(index, TEST_DIR "/file.bar", false);
 	check_status(g_repo, 1, 0, 0, 1, 0, 1, 1);
 
-	cl_git_mkfile("addall/file.zzz", "yet another one");
-	cl_git_mkfile("addall/other.zzz", "yet another one");
-	cl_git_mkfile("addall/more.zzz", "yet another one");
+	cl_git_mkfile(TEST_DIR "/file.zzz", "yet another one");
+	cl_git_mkfile(TEST_DIR "/other.zzz", "yet another one");
+	cl_git_mkfile(TEST_DIR "/more.zzz", "yet another one");
 	check_status(g_repo, 1, 0, 0, 4, 0, 1, 1);
 
 	cl_git_pass(git_index_update_all(index, NULL, NULL, NULL));
-	check_stat_data(index, "addall/file.bar", true);
+	check_stat_data(index, TEST_DIR "/file.bar", true);
 	check_status(g_repo, 1, 0, 0, 4, 0, 0, 1);
 
 	cl_git_pass(git_index_add_all(index, &paths, 0, NULL, NULL));
-	check_stat_data(index, "addall/file.zzz", true);
+	check_stat_data(index, TEST_DIR "/file.zzz", true);
 	check_status(g_repo, 2, 0, 0, 3, 0, 0, 1);
 
 	cl_repo_commit_from_index(NULL, g_repo, NULL, 0, "first commit");
@@ -195,27 +207,27 @@ void test_index_addall__repo_lifecycle(void)
 	/* add with force - should allow */
 	cl_git_pass(git_index_add_all(
 		index, &paths, GIT_INDEX_ADD_FORCE, NULL, NULL));
-	check_stat_data(index, "addall/file.foo", true);
+	check_stat_data(index, TEST_DIR "/file.foo", true);
 	check_status(g_repo, 1, 0, 0, 3, 0, 0, 0);
 
 	/* now it's in the index, so regular add should work */
-	cl_git_rewritefile("addall/file.foo", "new content for file");
-	check_stat_data(index, "addall/file.foo", false);
+	cl_git_rewritefile(TEST_DIR "/file.foo", "new content for file");
+	check_stat_data(index, TEST_DIR "/file.foo", false);
 	check_status(g_repo, 1, 0, 0, 3, 0, 1, 0);
 
 	cl_git_pass(git_index_add_all(index, &paths, 0, NULL, NULL));
-	check_stat_data(index, "addall/file.foo", true);
+	check_stat_data(index, TEST_DIR "/file.foo", true);
 	check_status(g_repo, 1, 0, 0, 3, 0, 0, 0);
 
 	cl_git_pass(git_index_add_bypath(index, "more.zzz"));
-	check_stat_data(index, "addall/more.zzz", true);
+	check_stat_data(index, TEST_DIR "/more.zzz", true);
 	check_status(g_repo, 2, 0, 0, 2, 0, 0, 0);
 
-	cl_git_rewritefile("addall/file.zzz", "new content for file");
+	cl_git_rewritefile(TEST_DIR "/file.zzz", "new content for file");
 	check_status(g_repo, 2, 0, 0, 2, 0, 1, 0);
 
 	cl_git_pass(git_index_add_bypath(index, "file.zzz"));
-	check_stat_data(index, "addall/file.zzz", true);
+	check_stat_data(index, TEST_DIR "/file.zzz", true);
 	check_status(g_repo, 2, 0, 1, 2, 0, 0, 0);
 
 	strs[0] = "*.zzz";
@@ -228,7 +240,7 @@ void test_index_addall__repo_lifecycle(void)
 	cl_repo_commit_from_index(NULL, g_repo, NULL, 0, "second commit");
 	check_status(g_repo, 0, 0, 0, 3, 0, 0, 0);
 
-	cl_must_pass(p_unlink("addall/file.zzz"));
+	cl_must_pass(p_unlink(TEST_DIR "/file.zzz"));
 	check_status(g_repo, 0, 0, 0, 3, 1, 0, 0);
 
 	/* update_all should be able to remove entries */
@@ -240,9 +252,9 @@ void test_index_addall__repo_lifecycle(void)
 	check_status(g_repo, 3, 1, 0, 0, 0, 0, 0);
 
 	/* must be able to remove at any position while still updating other files */
-	cl_must_pass(p_unlink("addall/.gitignore"));
-	cl_git_rewritefile("addall/file.zzz", "reconstructed file");
-	cl_git_rewritefile("addall/more.zzz", "altered file reality");
+	cl_must_pass(p_unlink(TEST_DIR "/.gitignore"));
+	cl_git_rewritefile(TEST_DIR "/file.zzz", "reconstructed file");
+	cl_git_rewritefile(TEST_DIR "/more.zzz", "altered file reality");
 	check_status(g_repo, 3, 1, 0, 1, 1, 1, 0);
 
 	cl_git_pass(git_index_update_all(index, NULL, NULL, NULL));
@@ -256,3 +268,89 @@ void test_index_addall__repo_lifecycle(void)
 
 	git_index_free(index);
 }
+
+static int addall_match_prefix(
+	const char *path, const char *matched_pathspec, void *payload)
+{
+	GIT_UNUSED(matched_pathspec);
+	return !git__prefixcmp(path, payload) ? 0 : 1;
+}
+
+static int addall_match_suffix(
+	const char *path, const char *matched_pathspec, void *payload)
+{
+	GIT_UNUSED(matched_pathspec);
+	return !git__suffixcmp(path, payload) ? 0 : 1;
+}
+
+static int addall_cancel_at(
+	const char *path, const char *matched_pathspec, void *payload)
+{
+	GIT_UNUSED(matched_pathspec);
+	return !strcmp(path, payload) ? -123 : 0;
+}
+
+void test_index_addall__callback_filtering(void)
+{
+	git_index *index;
+
+	addall_create_test_repo(false);
+
+	cl_git_pass(git_repository_index(&index, g_repo));
+
+	cl_git_pass(
+		git_index_add_all(index, NULL, 0, addall_match_prefix, "file."));
+	check_stat_data(index, TEST_DIR "/file.bar", true);
+	check_status(g_repo, 1, 0, 0, 1, 0, 0, 1);
+
+	cl_git_mkfile(TEST_DIR "/file.zzz", "yet another one");
+	cl_git_mkfile(TEST_DIR "/more.zzz", "yet another one");
+	cl_git_mkfile(TEST_DIR "/other.zzz", "yet another one");
+
+	cl_git_pass(git_index_update_all(index, NULL, NULL, NULL));
+	check_stat_data(index, TEST_DIR "/file.bar", true);
+	check_status(g_repo, 1, 0, 0, 4, 0, 0, 1);
+
+	cl_git_pass(
+		git_index_add_all(index, NULL, 0, addall_match_prefix, "other"));
+	check_stat_data(index, TEST_DIR "/other.zzz", true);
+	check_status(g_repo, 2, 0, 0, 3, 0, 0, 1);
+
+	cl_git_pass(
+		git_index_add_all(index, NULL, 0, addall_match_suffix, ".zzz"));
+	check_status(g_repo, 4, 0, 0, 1, 0, 0, 1);
+
+	cl_git_pass(
+		git_index_remove_all(index, NULL, addall_match_suffix, ".zzz"));
+	check_status(g_repo, 1, 0, 0, 4, 0, 0, 1);
+
+	cl_git_fail_with(
+		git_index_add_all(index, NULL, 0, addall_cancel_at, "more.zzz"), -123);
+	check_status(g_repo, 3, 0, 0, 2, 0, 0, 1);
+
+	cl_git_fail_with(
+		git_index_add_all(index, NULL, 0, addall_cancel_at, "other.zzz"), -123);
+	check_status(g_repo, 4, 0, 0, 1, 0, 0, 1);
+
+	cl_git_pass(
+		git_index_add_all(index, NULL, 0, addall_match_suffix, ".zzz"));
+	check_status(g_repo, 5, 0, 0, 0, 0, 0, 1);
+
+	cl_must_pass(p_unlink(TEST_DIR "/file.zzz"));
+	cl_must_pass(p_unlink(TEST_DIR "/more.zzz"));
+	cl_must_pass(p_unlink(TEST_DIR "/other.zzz"));
+
+	cl_git_fail_with(
+		git_index_update_all(index, NULL, addall_cancel_at, "more.zzz"), -123);
+	/* file.zzz removed from index (so Index Adds 5 -> 4) and
+	 * more.zzz + other.zzz removed (so Worktree Dels 0 -> 2) */
+	check_status(g_repo, 4, 0, 0, 0, 2, 0, 1);
+
+	cl_git_fail_with(
+		git_index_update_all(index, NULL, addall_cancel_at, "other.zzz"), -123);
+	/* more.zzz removed from index (so Index Adds 4 -> 3) and
+	 * Just other.zzz removed (so Worktree Dels 2 -> 1) */
+	check_status(g_repo, 3, 0, 0, 0, 1, 0, 1);
+
+	git_index_free(index);
+}
diff --git a/tests/notes/notes.c b/tests/notes/notes.c
index 82dcaf8ca..c2579a2c4 100644
--- a/tests/notes/notes.c
+++ b/tests/notes/notes.c
@@ -129,7 +129,7 @@ void test_notes_notes__can_cancel_foreach(void)
 	create_note(&note_oid4, "refs/notes/i-can-see-dead-notes", "4a202b346bb0fb0db7eff3cffeb3c70babbd2045", "I decorate 9fd7 and 4a20\n");
 
 	cl_assert_equal_i(
-		GIT_EUSER,
+		1,
 		git_note_foreach(_repo, "refs/notes/i-can-see-dead-notes",
 			note_cancel_cb, &retrieved_notes));
 }
diff --git a/tests/object/blob/fromchunks.c b/tests/object/blob/fromchunks.c
index 03ed4efb4..b61cabfe1 100644
--- a/tests/object/blob/fromchunks.c
+++ b/tests/object/blob/fromchunks.c
@@ -59,7 +59,7 @@ void test_object_blob_fromchunks__doesnot_overwrite_an_already_existing_object(v
 	git_buf content = GIT_BUF_INIT;
 	git_oid expected_oid, oid;
 	int howmany = 7;
-	
+
 	cl_git_pass(git_oid_fromstr(&expected_oid, "321cbdf08803c744082332332838df6bd160f8f9"));
 
 	cl_git_pass(git_blob_create_fromchunks(&oid, repo, NULL, text_chunked_source_cb, &howmany));
@@ -117,3 +117,40 @@ void test_object_blob_fromchunks__creating_a_blob_from_chunks_honors_the_attribu
 	assert_named_chunked_blob("e9671e138a780833cb689753570fd10a55be84fb", "dummy.txt");
 	assert_named_chunked_blob("e9671e138a780833cb689753570fd10a55be84fb", "dummy.dunno");
 }
+
+static int failing_chunked_source_cb(
+	char *content, size_t max_length, void *payload)
+{
+	int *count = (int *)payload;
+
+	GIT_UNUSED(max_length);
+
+	(*count)--;
+	if (*count == 0)
+		return -1234;
+
+	strcpy(content, textual_content);
+	return (int)strlen(textual_content);
+}
+
+void test_object_blob_fromchunks__can_stop_with_error(void)
+{
+	git_oid expected_oid, oid;
+	git_object *blob;
+	int howmany = 7;
+
+	cl_git_pass(git_oid_fromstr(
+		&expected_oid, "321cbdf08803c744082332332838df6bd160f8f9"));
+
+	cl_git_fail_with(
+		git_object_lookup(&blob, repo, &expected_oid, GIT_OBJ_ANY),
+		GIT_ENOTFOUND);
+
+	cl_git_fail_with(git_blob_create_fromchunks(
+		&oid, repo, NULL, failing_chunked_source_cb, &howmany), -1234);
+
+	cl_git_fail_with(
+		git_object_lookup(&blob, repo, &expected_oid, GIT_OBJ_ANY),
+		GIT_ENOTFOUND);
+}
+
diff --git a/tests/object/tree/walk.c b/tests/object/tree/walk.c
index 1207e864c..f8005e579 100644
--- a/tests/object/tree/walk.c
+++ b/tests/object/tree/walk.c
@@ -59,7 +59,7 @@ static int treewalk_stop_cb(
 
 	(*count) += 1;
 
-	return (*count == 2) ? -1 : 0;
+	return (*count == 2) ? -123 : 0;
 }
 
 static int treewalk_stop_immediately_cb(
@@ -83,20 +83,20 @@ void test_object_tree_walk__1(void)
 
 	ct = 0;
 	cl_assert_equal_i(
-		GIT_EUSER, git_tree_walk(tree, GIT_TREEWALK_PRE, treewalk_stop_cb, &ct));
+		-123, git_tree_walk(tree, GIT_TREEWALK_PRE, treewalk_stop_cb, &ct));
 	cl_assert_equal_i(2, ct);
 
 	ct = 0;
 	cl_assert_equal_i(
-		GIT_EUSER, git_tree_walk(tree, GIT_TREEWALK_POST, treewalk_stop_cb, &ct));
+		-123, git_tree_walk(tree, GIT_TREEWALK_POST, treewalk_stop_cb, &ct));
 	cl_assert_equal_i(2, ct);
 
 	cl_assert_equal_i(
-		GIT_EUSER, git_tree_walk(
+		-100, git_tree_walk(
 			tree, GIT_TREEWALK_PRE, treewalk_stop_immediately_cb, NULL));
 
 	cl_assert_equal_i(
-		GIT_EUSER, git_tree_walk(
+		-100, git_tree_walk(
 			tree, GIT_TREEWALK_POST, treewalk_stop_immediately_cb, NULL));
 
 	git_tree_free(tree);
@@ -152,7 +152,7 @@ void test_object_tree_walk__2(void)
 	memset(&data, 0, sizeof(data));
 	data.stop = "3.txt";
 
-	cl_assert_equal_i(GIT_EUSER, git_tree_walk(
+	cl_assert_equal_i(-1, git_tree_walk(
 		tree, GIT_TREEWALK_PRE, treewalk_skip_de_cb, &data));
 	cl_assert_equal_i(3, data.files);
 	cl_assert_equal_i(2, data.dirs);
@@ -168,7 +168,7 @@ void test_object_tree_walk__2(void)
 	memset(&data, 0, sizeof(data));
 	data.stop = "new.txt";
 
-	cl_assert_equal_i(GIT_EUSER, git_tree_walk(
+	cl_assert_equal_i(-1, git_tree_walk(
 		tree, GIT_TREEWALK_PRE, treewalk_skip_de_cb, &data));
 	cl_assert_equal_i(7, data.files);
 	cl_assert_equal_i(4, data.dirs);
diff --git a/tests/object/tree/write.c b/tests/object/tree/write.c
index 468c0ccd1..3bea0ed4d 100644
--- a/tests/object/tree/write.c
+++ b/tests/object/tree/write.c
@@ -164,24 +164,25 @@ void test_object_tree_write__sorted_subtrees(void)
 	git_treebuilder_free(builder);
 }
 
+static struct {
+	unsigned int attr;
+	const char *filename;
+} _entries[] = {
+	{ GIT_FILEMODE_BLOB, "aardvark" },
+	{ GIT_FILEMODE_BLOB, ".first" },
+	{ GIT_FILEMODE_BLOB, "apple" },
+	{ GIT_FILEMODE_BLOB, "last"},
+	{ GIT_FILEMODE_BLOB, "apple_after"},
+	{ GIT_FILEMODE_BLOB, "after_aardvark"},
+	{ 0, NULL },
+};
+
 void test_object_tree_write__removing_and_re_adding_in_treebuilder(void)
 {
 	git_treebuilder *builder;
-	int i,  aardvark_i, apple_i, apple_after_i, apple_extra_i, last_i;
+	int i, aardvark_i, apple_i, apple_after_i, apple_extra_i, last_i;
 	git_oid blank_oid, tree_oid;
 	git_tree *tree;
-	struct {
-		unsigned int attr;
-		const char *filename;
-	} entries[] = {
-		{ GIT_FILEMODE_BLOB, "aardvark" },
-		{ GIT_FILEMODE_BLOB, ".first" },
-		{ GIT_FILEMODE_BLOB, "apple" },
-		{ GIT_FILEMODE_BLOB, "last"},
-		{ GIT_FILEMODE_BLOB, "apple_after"},
-		{ GIT_FILEMODE_BLOB, "after_aardvark"},
-		{ 0, NULL },
-	};
 
 	memset(&blank_oid, 0x0, sizeof(blank_oid));
 
@@ -189,9 +190,9 @@ void test_object_tree_write__removing_and_re_adding_in_treebuilder(void)
 
 	cl_assert_equal_i(0, (int)git_treebuilder_entrycount(builder));
 
-	for (i = 0; entries[i].filename; ++i)
+	for (i = 0; _entries[i].filename; ++i)
 		cl_git_pass(git_treebuilder_insert(NULL,
-			builder, entries[i].filename, &blank_oid, entries[i].attr));
+			builder, _entries[i].filename, &blank_oid, _entries[i].attr));
 
 	cl_assert_equal_i(6, (int)git_treebuilder_entrycount(builder));
 
@@ -260,3 +261,56 @@ void test_object_tree_write__removing_and_re_adding_in_treebuilder(void)
 
 	git_tree_free(tree);
 }
+
+static int treebuilder_filter_prefixed(
+	const git_tree_entry *entry, void *payload)
+{
+	return !git__prefixcmp(git_tree_entry_name(entry), payload);
+}
+
+void test_object_tree_write__filtering(void)
+{
+	git_treebuilder *builder;
+	int i;
+	git_oid blank_oid, tree_oid;
+	git_tree *tree;
+
+	memset(&blank_oid, 0x0, sizeof(blank_oid));
+
+	cl_git_pass(git_treebuilder_create(&builder, NULL));
+
+	for (i = 0; _entries[i].filename; ++i)
+		cl_git_pass(git_treebuilder_insert(NULL,
+			builder, _entries[i].filename, &blank_oid, _entries[i].attr));
+
+	cl_assert_equal_i(6, (int)git_treebuilder_entrycount(builder));
+
+	cl_assert(git_treebuilder_get(builder, "apple") != NULL);
+	cl_assert(git_treebuilder_get(builder, "aardvark") != NULL);
+	cl_assert(git_treebuilder_get(builder, "last") != NULL);
+
+	git_treebuilder_filter(builder, treebuilder_filter_prefixed, "apple");
+
+	cl_assert_equal_i(4, (int)git_treebuilder_entrycount(builder));
+
+	cl_assert(git_treebuilder_get(builder, "apple") == NULL);
+	cl_assert(git_treebuilder_get(builder, "aardvark") != NULL);
+	cl_assert(git_treebuilder_get(builder, "last") != NULL);
+
+	git_treebuilder_filter(builder, treebuilder_filter_prefixed, "a");
+
+	cl_assert_equal_i(2, (int)git_treebuilder_entrycount(builder));
+
+	cl_assert(git_treebuilder_get(builder, "aardvark") == NULL);
+	cl_assert(git_treebuilder_get(builder, "last") != NULL);
+
+	cl_git_pass(git_treebuilder_write(&tree_oid, g_repo, builder));
+
+	git_treebuilder_free(builder);
+
+	cl_git_pass(git_tree_lookup(&tree, g_repo, &tree_oid));
+
+	cl_assert_equal_i(2, (int)git_tree_entrycount(tree));
+
+	git_tree_free(tree);
+}
diff --git a/tests/odb/foreach.c b/tests/odb/foreach.c
index ebb8866f7..256ae9cd7 100644
--- a/tests/odb/foreach.c
+++ b/tests/odb/foreach.c
@@ -5,7 +5,6 @@
 
 static git_odb *_odb;
 static git_repository *_repo;
-static int nobj;
 
 void test_odb_foreach__cleanup(void)
 {
@@ -18,10 +17,10 @@ void test_odb_foreach__cleanup(void)
 
 static int foreach_cb(const git_oid *oid, void *data)
 {
-	GIT_UNUSED(data);
-	GIT_UNUSED(oid);
+	int *nobj = data;
+	(*nobj)++;
 
-	nobj++;
+	GIT_UNUSED(oid);
 
 	return 0;
 }
@@ -38,43 +37,46 @@ static int foreach_cb(const git_oid *oid, void *data)
  */
 void test_odb_foreach__foreach(void)
 {
+	int nobj = 0;
+
 	cl_git_pass(git_repository_open(&_repo, cl_fixture("testrepo.git")));
 	git_repository_odb(&_odb, _repo);
 
-	cl_git_pass(git_odb_foreach(_odb, foreach_cb, NULL));
+	cl_git_pass(git_odb_foreach(_odb, foreach_cb, &nobj));
 	cl_assert_equal_i(47 + 1640, nobj); /* count + in-pack */
 }
 
 void test_odb_foreach__one_pack(void)
 {
 	git_odb_backend *backend = NULL;
+	int nobj = 0;
 
 	cl_git_pass(git_odb_new(&_odb));
 	cl_git_pass(git_odb_backend_one_pack(&backend, cl_fixture("testrepo.git/objects/pack/pack-a81e489679b7d3418f9ab594bda8ceb37dd4c695.idx")));
 	cl_git_pass(git_odb_add_backend(_odb, backend, 1));
 	_repo = NULL;
 
-	nobj = 0;
-	cl_git_pass(git_odb_foreach(_odb, foreach_cb, NULL));
+	cl_git_pass(git_odb_foreach(_odb, foreach_cb, &nobj));
 	cl_assert(nobj == 1628);
 }
 
 static int foreach_stop_cb(const git_oid *oid, void *data)
 {
-	GIT_UNUSED(data);
-	GIT_UNUSED(oid);
+	int *nobj = data;
+	(*nobj)++;
 
-	nobj++;
+	GIT_UNUSED(oid);
 
-	return (nobj == 1000);
+	return (*nobj == 1000) ? -321 : 0;
 }
 
 void test_odb_foreach__interrupt_foreach(void)
 {
-	nobj = 0;
+	int nobj = 0;
+
 	cl_git_pass(git_repository_open(&_repo, cl_fixture("testrepo.git")));
 	git_repository_odb(&_odb, _repo);
 
-	cl_assert_equal_i(GIT_EUSER, git_odb_foreach(_odb, foreach_stop_cb, NULL));
+	cl_assert_equal_i(-321, git_odb_foreach(_odb, foreach_stop_cb, &nobj));
 	cl_assert(nobj == 1000);
 }
diff --git a/tests/online/clone.c b/tests/online/clone.c
index efc76d958..be4421ae5 100644
--- a/tests/online/clone.c
+++ b/tests/online/clone.c
@@ -273,7 +273,7 @@ static int cancel_at_half(const git_transfer_progress *stats, void *payload)
 	GIT_UNUSED(payload);
 
 	if (stats->received_objects > (stats->total_objects/2))
-		return 1;
+		return 4321;
 	return 0;
 }
 
@@ -281,7 +281,8 @@ void test_online_clone__can_cancel(void)
 {
 	g_options.remote_callbacks.transfer_progress = cancel_at_half;
 
-	cl_git_fail_with(git_clone(&g_repo, LIVE_REPO_URL, "./foo", &g_options), GIT_EUSER);
+	cl_git_fail_with(
+		git_clone(&g_repo, LIVE_REPO_URL, "./foo", &g_options), 4321);
 }
 
 
diff --git a/tests/online/fetch.c b/tests/online/fetch.c
index 5153a7ae0..7e9dfdbbe 100644
--- a/tests/online/fetch.c
+++ b/tests/online/fetch.c
@@ -129,7 +129,7 @@ static int cancel_at_half(const git_transfer_progress *stats, void *payload)
 	GIT_UNUSED(payload);
 
 	if (stats->received_objects > (stats->total_objects/2))
-		return -1;
+		return -4321;
 	return 0;
 }
 
@@ -147,7 +147,7 @@ void test_online_fetch__can_cancel(void)
 	git_remote_set_callbacks(remote, &callbacks);
 
 	cl_git_pass(git_remote_connect(remote, GIT_DIRECTION_FETCH));
-	cl_git_fail_with(git_remote_download(remote), GIT_EUSER);
+	cl_git_fail_with(git_remote_download(remote), -4321);
 	git_remote_disconnect(remote);
 	git_remote_free(remote);
 }
diff --git a/tests/online/push.c b/tests/online/push.c
index be505c3a1..33f174654 100644
--- a/tests/online/push.c
+++ b/tests/online/push.c
@@ -207,6 +207,7 @@ static void verify_tracking_branches(git_remote *remote, expected_ref expected_r
 	}
 
 	cl_assert_equal_i(error, GIT_ITEROVER);
+	git_branch_iterator_free(iter);
 
 	/* Loop through expected refs, make sure they exist */
 	for (i = 0; i < expected_refs_len; i++) {
@@ -371,19 +372,25 @@ void test_online_push__cleanup(void)
 	cl_git_sandbox_cleanup();
 }
 
-static int push_pack_progress_cb(int stage, unsigned int current, unsigned int total, void* payload)
+static int push_pack_progress_cb(
+	int stage, unsigned int current, unsigned int total, void* payload)
 {
-	int *was_called = (int *) payload;
+	int *calls = (int *)payload;
 	GIT_UNUSED(stage); GIT_UNUSED(current); GIT_UNUSED(total);
-	*was_called = 1;
+	if (*calls < 0)
+		return *calls;
+	(*calls)++;
 	return 0;
 }
 
-static int push_transfer_progress_cb(unsigned int current, unsigned int total, size_t bytes, void* payload)
+static int push_transfer_progress_cb(
+	unsigned int current, unsigned int total, size_t bytes, void* payload)
 {
-	int *was_called = (int *) payload;
+	int *calls = (int *)payload;
 	GIT_UNUSED(current); GIT_UNUSED(total); GIT_UNUSED(bytes);
-	*was_called = 1;
+	if (*calls < 0)
+		return *calls;
+	(*calls)++;
 	return 0;
 }
 
@@ -397,15 +404,16 @@ static int push_transfer_progress_cb(unsigned int current, unsigned int total, s
  * @param expected_ret expected return value from git_push_finish()
  * @param check_progress_cb Check that the push progress callbacks are called
  */
-static void do_push(const char *refspecs[], size_t refspecs_len,
+static void do_push(
+	const char *refspecs[], size_t refspecs_len,
 	push_status expected_statuses[], size_t expected_statuses_len,
-	expected_ref expected_refs[], size_t expected_refs_len, int expected_ret, int check_progress_cb)
+	expected_ref expected_refs[], size_t expected_refs_len,
+	int expected_ret, int check_progress_cb)
 {
 	git_push *push;
 	git_push_options opts = GIT_PUSH_OPTIONS_INIT;
 	size_t i;
-	int ret;
-	int pack_progress_called = 0, transfer_progress_called = 0;
+	int pack_progress_calls = 0, transfer_progress_calls = 0;
 
 	if (_remote) {
 		/* Auto-detect the number of threads to use */
@@ -416,30 +424,35 @@ static void do_push(const char *refspecs[], size_t refspecs_len,
 		cl_git_pass(git_push_new(&push, _remote));
 		cl_git_pass(git_push_set_options(push, &opts));
 
-		if (check_progress_cb)
-			cl_git_pass(git_push_set_callbacks(push, push_pack_progress_cb, &pack_progress_called, push_transfer_progress_cb, &transfer_progress_called));
+		if (check_progress_cb) {
+			/* if EUSER, then abort in transfer */
+			if (expected_ret == GIT_EUSER)
+				transfer_progress_calls = GIT_EUSER;
+
+			cl_git_pass(
+				git_push_set_callbacks(
+					push, push_pack_progress_cb, &pack_progress_calls,
+					push_transfer_progress_cb, &transfer_progress_calls));
+		}
 
 		for (i = 0; i < refspecs_len; i++)
 			cl_git_pass(git_push_add_refspec(push, refspecs[i]));
 
 		if (expected_ret < 0) {
-			cl_git_fail(ret = git_push_finish(push));
+			cl_git_fail_with(git_push_finish(push), expected_ret);
 			cl_assert_equal_i(0, git_push_unpack_ok(push));
-		}
-		else {
-			cl_git_pass(ret = git_push_finish(push));
+		} else {
+			cl_git_pass(git_push_finish(push));
 			cl_assert_equal_i(1, git_push_unpack_ok(push));
 		}
 
-		if (check_progress_cb) {
-			cl_assert_equal_i(1, pack_progress_called);
-			cl_assert_equal_i(1, transfer_progress_called);
+		if (check_progress_cb && !expected_ret) {
+			cl_assert(pack_progress_calls > 0);
+			cl_assert(transfer_progress_calls > 0);
 		}
 
 		do_verify_push_status(push, expected_statuses, expected_statuses_len);
 
-		cl_assert_equal_i(expected_ret, ret);
-
 		verify_refs(_remote, expected_refs, expected_refs_len);
 
 		cl_git_pass(git_push_update_tips(push));
@@ -507,6 +520,12 @@ void test_online_push__b5(void)
 		exp_refs, ARRAY_SIZE(exp_refs), 0, 1);
 }
 
+void test_online_push__b5_cancel(void)
+{
+	const char *specs[] = { "refs/heads/b5:refs/heads/b5" };
+	do_push(specs, ARRAY_SIZE(specs), NULL, 0, NULL, 0, GIT_EUSER, 1);
+}
+
 void test_online_push__multi(void)
 {
 	const char *specs[] = {
@@ -731,7 +750,7 @@ void test_online_push__bad_refspecs(void)
 	git_push *push;
 
 	if (_remote) {
-//		cl_git_pass(git_remote_connect(_remote, GIT_DIRECTION_PUSH));
+/*		cl_git_pass(git_remote_connect(_remote, GIT_DIRECTION_PUSH)); */
 		cl_git_pass(git_push_new(&push, _remote));
 
 		/* Unexpanded branch names not supported */
diff --git a/tests/pack/indexer.c b/tests/pack/indexer.c
index 07963a9e7..084f8e666 100644
--- a/tests/pack/indexer.c
+++ b/tests/pack/indexer.c
@@ -11,7 +11,7 @@
  * This is a packfile with three objects. The second is a delta which
  * depends on the third, which is also a delta.
  */
-unsigned char out_of_order_pack[] = {
+static const unsigned char out_of_order_pack[] = {
   0x50, 0x41, 0x43, 0x4b, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x03,
   0x32, 0x78, 0x9c, 0x63, 0x67, 0x00, 0x00, 0x00, 0x10, 0x00, 0x08, 0x76,
   0xe6, 0x8f, 0xe8, 0x12, 0x9b, 0x54, 0x6b, 0x10, 0x1a, 0xee, 0x95, 0x10,
@@ -23,13 +23,13 @@ unsigned char out_of_order_pack[] = {
   0x19, 0x87, 0x58, 0x80, 0x61, 0x09, 0x9a, 0x33, 0xca, 0x7a, 0x31, 0x92,
   0x6f, 0xae, 0x66, 0x75
 };
-unsigned int out_of_order_pack_len = 112;
+static const unsigned int out_of_order_pack_len = 112;
 
 /*
  * Packfile with two objects. The second is a delta against an object
  * which is not in the packfile
  */
-unsigned char thin_pack[] = {
+static const unsigned char thin_pack[] = {
   0x50, 0x41, 0x43, 0x4b, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x02,
   0x32, 0x78, 0x9c, 0x63, 0x67, 0x00, 0x00, 0x00, 0x10, 0x00, 0x08, 0x76,
   0xe6, 0x8f, 0xe8, 0x12, 0x9b, 0x54, 0x6b, 0x10, 0x1a, 0xee, 0x95, 0x10,
@@ -38,18 +38,19 @@ unsigned char thin_pack[] = {
   0x3a, 0x6f, 0x39, 0xd1, 0xfe, 0x66, 0x68, 0x6b, 0xa5, 0xe5, 0xe2, 0x97,
   0xac, 0x94, 0x6c, 0x76, 0x0b, 0x04
 };
-unsigned int thin_pack_len = 78;
+static const unsigned int thin_pack_len = 78;
 
-unsigned char base_obj[] = { 07, 076 };
-unsigned int base_obj_len = 2;
+static const unsigned char base_obj[] = { 07, 076 };
+static const unsigned int base_obj_len = 2;
 
 void test_pack_indexer__out_of_order(void)
 {
-	git_indexer *idx;
-	git_transfer_progress stats;
+	git_indexer *idx = 0;
+	git_transfer_progress stats = { 0 };
 
 	cl_git_pass(git_indexer_new(&idx, ".", 0, NULL, NULL, NULL));
-	cl_git_pass(git_indexer_append(idx, out_of_order_pack, out_of_order_pack_len, &stats));
+	cl_git_pass(git_indexer_append(
+		idx, out_of_order_pack, out_of_order_pack_len, &stats));
 	cl_git_pass(git_indexer_commit(idx, &stats));
 
 	cl_assert_equal_i(stats.total_objects, 3);
@@ -61,8 +62,8 @@ void test_pack_indexer__out_of_order(void)
 
 void test_pack_indexer__fix_thin(void)
 {
-	git_indexer *idx;
-	git_transfer_progress stats;
+	git_indexer *idx = NULL;
+	git_transfer_progress stats = { 0 };
 	git_repository *repo;
 	git_odb *odb;
 	git_oid id, should_id;
diff --git a/tests/pack/packbuilder.c b/tests/pack/packbuilder.c
index 1ae2322a5..53db81828 100644
--- a/tests/pack/packbuilder.c
+++ b/tests/pack/packbuilder.c
@@ -12,6 +12,7 @@ static git_packbuilder *_packbuilder;
 static git_indexer *_indexer;
 static git_vector _commits;
 static int _commits_is_initialized;
+static git_transfer_progress _stats;
 
 void test_pack_packbuilder__initialize(void)
 {
@@ -20,6 +21,7 @@ void test_pack_packbuilder__initialize(void)
 	cl_git_pass(git_packbuilder_new(&_packbuilder, _repo));
 	cl_git_pass(git_vector_init(&_commits, 0, NULL));
 	_commits_is_initialized = 1;
+	memset(&_stats, 0, sizeof(_stats));
 }
 
 void test_pack_packbuilder__cleanup(void)
@@ -184,11 +186,10 @@ void test_pack_packbuilder__permissions_readwrite(void)
 	test_write_pack_permission(0666, 0666);
 }
 
-static git_transfer_progress stats;
 static int foreach_cb(void *buf, size_t len, void *payload)
 {
 	git_indexer *idx = (git_indexer *) payload;
-	cl_git_pass(git_indexer_append(idx, buf, len, &stats));
+	cl_git_pass(git_indexer_append(idx, buf, len, &_stats));
 	return 0;
 }
 
@@ -199,6 +200,24 @@ void test_pack_packbuilder__foreach(void)
 	seed_packbuilder();
 	cl_git_pass(git_indexer_new(&idx, ".", 0, NULL, NULL, NULL));
 	cl_git_pass(git_packbuilder_foreach(_packbuilder, foreach_cb, idx));
-	cl_git_pass(git_indexer_commit(idx, &stats));
+	cl_git_pass(git_indexer_commit(idx, &_stats));
+	git_indexer_free(idx);
+}
+
+static int foreach_cancel_cb(void *buf, size_t len, void *payload)
+{
+	git_indexer *idx = (git_indexer *)payload;
+	cl_git_pass(git_indexer_append(idx, buf, len, &_stats));
+	return (_stats.total_objects > 2) ? -1111 : 0;
+}
+
+void test_pack_packbuilder__foreach_with_cancel(void)
+{
+	git_indexer *idx;
+
+	seed_packbuilder();
+	cl_git_pass(git_indexer_new(&idx, ".", 0, NULL, NULL, NULL));
+	cl_git_fail_with(
+		git_packbuilder_foreach(_packbuilder, foreach_cancel_cb, idx), -1111);
 	git_indexer_free(idx);
 }
diff --git a/tests/refs/branches/move.c b/tests/refs/branches/move.c
index ecf14e006..9d233de1a 100644
--- a/tests/refs/branches/move.c
+++ b/tests/refs/branches/move.c
@@ -66,12 +66,54 @@ void test_refs_branches_move__can_move_a_local_branch_to_a_partially_colliding_n
 void test_refs_branches_move__can_not_move_a_branch_if_its_destination_name_collide_with_an_existing_one(void)
 {
 	git_reference *original_ref, *new_ref;
+	git_config *config;
+	const git_config_entry *ce;
+	char *original_remote, *original_merge;
+
+	cl_git_pass(git_repository_config(&config, repo));
+
+	cl_git_pass(git_config_get_entry(&ce, config, "branch.master.remote"));
+	original_remote = strdup(ce->value);
+	cl_git_pass(git_config_get_entry(&ce, config, "branch.master.merge"));
+	original_merge  = strdup(ce->value);
+
 
 	cl_git_pass(git_reference_lookup(&original_ref, repo, "refs/heads/br2"));
 
-	cl_assert_equal_i(GIT_EEXISTS, git_branch_move(&new_ref, original_ref, "master", 0));
+	cl_assert_equal_i(GIT_EEXISTS,
+		git_branch_move(&new_ref, original_ref, "master", 0));
+
+	cl_assert(giterr_last()->message != NULL);
+	cl_git_pass(git_config_get_entry(&ce, config, "branch.master.remote"));
+	cl_assert_equal_s(original_remote, ce->value);
+	cl_git_pass(git_config_get_entry(&ce, config, "branch.master.merge"));
+	cl_assert_equal_s(original_merge,  ce->value);
+
+
+	cl_assert_equal_i(GIT_EEXISTS,
+		git_branch_move(&new_ref, original_ref, "cannot-fetch", 0));
+
+	cl_assert(giterr_last()->message != NULL);
+	cl_git_pass(git_config_get_entry(&ce, config, "branch.master.remote"));
+	cl_assert_equal_s(original_remote, ce->value);
+	cl_git_pass(git_config_get_entry(&ce, config, "branch.master.merge"));
+	cl_assert_equal_s(original_merge,  ce->value);
+
+	git_reference_free(original_ref);
+	cl_git_pass(git_reference_lookup(&original_ref, repo, "refs/heads/track-local"));
+
+	cl_assert_equal_i(GIT_EEXISTS,
+		git_branch_move(&new_ref, original_ref, "master", 0));
+
+	cl_assert(giterr_last()->message != NULL);
+	cl_git_pass(git_config_get_entry(&ce, config, "branch.master.remote"));
+	cl_assert_equal_s(original_remote, ce->value);
+	cl_git_pass(git_config_get_entry(&ce, config, "branch.master.merge"));
+	cl_assert_equal_s(original_merge,  ce->value);
 
+	free(original_remote); free(original_merge);
 	git_reference_free(original_ref);
+	git_config_free(config);
 }
 
 void test_refs_branches_move__moving_a_branch_with_an_invalid_name_returns_EINVALIDSPEC(void)
diff --git a/tests/refs/foreachglob.c b/tests/refs/foreachglob.c
index 2c458082f..c0f6ce763 100644
--- a/tests/refs/foreachglob.c
+++ b/tests/refs/foreachglob.c
@@ -81,14 +81,14 @@ static int interrupt_cb(const char *reference_name, void *payload)
 
 	(*count)++;
 
-	return (*count == 11);
+	return (*count == 11) ? -1000 : 0;
 }
 
 void test_refs_foreachglob__can_cancel(void)
 {
 	int count = 0;
 
-	cl_assert_equal_i(GIT_EUSER, git_reference_foreach_glob(
+	cl_assert_equal_i(-1000, git_reference_foreach_glob(
 		repo, "*", interrupt_cb, &count) );
 
 	cl_assert_equal_i(11, count);
diff --git a/tests/refs/iterator.c b/tests/refs/iterator.c
index 266410fdf..a29b0cf8b 100644
--- a/tests/refs/iterator.c
+++ b/tests/refs/iterator.c
@@ -46,36 +46,43 @@ static int refcmp_cb(const void *a, const void *b)
 	return strcmp(refa->name, refb->name);
 }
 
+static void assert_all_refnames_match(git_vector *output)
+{
+	size_t i;
+	git_reference *ref;
+
+	cl_assert_equal_sz(output->length, ARRAY_SIZE(refnames));
+
+	git_vector_sort(output);
+
+	git_vector_foreach(output, i, ref) {
+		cl_assert_equal_s(ref->name, refnames[i]);
+		git_reference_free(ref);
+	}
+
+	git_vector_free(output);
+}
+
 void test_refs_iterator__list(void)
 {
 	git_reference_iterator *iter;
 	git_vector output;
 	git_reference *ref;
-	int error;
-	size_t i;
 
 	cl_git_pass(git_vector_init(&output, 32, &refcmp_cb));
 	cl_git_pass(git_reference_iterator_new(&iter, repo));
 
-	do {
-		error = git_reference_next(&ref, iter);
-		cl_assert(error == 0 || error == GIT_ITEROVER);
-		if (error != GIT_ITEROVER) {
-			cl_git_pass(git_vector_insert(&output, ref));
-		}
-	} while (!error);
+	while (1) {
+		int error = git_reference_next(&ref, iter);
+		if (error == GIT_ITEROVER)
+			break;
+		cl_git_pass(error);
+		cl_git_pass(git_vector_insert(&output, ref));
+	}
 
 	git_reference_iterator_free(iter);
-	cl_assert_equal_sz(output.length, ARRAY_SIZE(refnames));
 
-	git_vector_sort(&output);
-
-	git_vector_foreach(&output, i, ref) {
-		cl_assert_equal_s(ref->name, refnames[i]);
-		git_reference_free(ref);
-	}
-
-	git_vector_free(&output);
+	assert_all_refnames_match(&output);
 }
 
 void test_refs_iterator__empty(void)
@@ -95,3 +102,87 @@ void test_refs_iterator__empty(void)
 	git_odb_free(odb);
 	git_repository_free(empty);
 }
+
+static int refs_foreach_cb(git_reference *reference, void *payload)
+{
+	git_vector *output = payload;
+	cl_git_pass(git_vector_insert(output, reference));
+	return 0;
+}
+
+void test_refs_iterator__foreach(void)
+{
+	git_vector output;
+	cl_git_pass(git_vector_init(&output, 32, &refcmp_cb));
+	cl_git_pass(git_reference_foreach(repo, refs_foreach_cb, &output));
+	assert_all_refnames_match(&output);
+}
+
+static int refs_foreach_cancel_cb(git_reference *reference, void *payload)
+{
+	int *cancel_after = payload;
+
+	git_reference_free(reference);
+
+	if (!*cancel_after)
+		return -333;
+	(*cancel_after)--;
+	return 0;
+}
+
+void test_refs_iterator__foreach_can_cancel(void)
+{
+	int cancel_after = 3;
+	cl_git_fail_with(
+		git_reference_foreach(repo, refs_foreach_cancel_cb, &cancel_after),
+		-333);
+	cl_assert_equal_i(0, cancel_after);
+}
+
+static int refs_foreach_name_cb(const char *name, void *payload)
+{
+	git_vector *output = payload;
+	cl_git_pass(git_vector_insert(output, git__strdup(name)));
+	return 0;
+}
+
+void test_refs_iterator__foreach_name(void)
+{
+	git_vector output;
+	size_t i;
+	char *name;
+
+	cl_git_pass(git_vector_init(&output, 32, &git__strcmp_cb));
+	cl_git_pass(
+		git_reference_foreach_name(repo, refs_foreach_name_cb, &output));
+
+	cl_assert_equal_sz(output.length, ARRAY_SIZE(refnames));
+	git_vector_sort(&output);
+
+	git_vector_foreach(&output, i, name) {
+		cl_assert_equal_s(name, refnames[i]);
+		git__free(name);
+	}
+
+	git_vector_free(&output);
+}
+
+static int refs_foreach_name_cancel_cb(const char *name, void *payload)
+{
+	int *cancel_after = payload;
+	if (!*cancel_after)
+		return -333;
+	GIT_UNUSED(name);
+	(*cancel_after)--;
+	return 0;
+}
+
+void test_refs_iterator__foreach_name_can_cancel(void)
+{
+	int cancel_after = 5;
+	cl_git_fail_with(
+		git_reference_foreach_name(
+			repo, refs_foreach_name_cancel_cb, &cancel_after),
+		-333);
+	cl_assert_equal_i(0, cancel_after);
+}
diff --git a/tests/status/worktree.c b/tests/status/worktree.c
index 34be6d34c..fd57fcc1e 100644
--- a/tests/status/worktree.c
+++ b/tests/status/worktree.c
@@ -552,7 +552,7 @@ static int cb_status__interrupt(const char *p, unsigned int s, void *payload)
 
 	(*count)++;
 
-	return (*count == 8);
+	return (*count == 8) ? -111 : 0;
 }
 
 void test_status_worktree__interruptable_foreach(void)
@@ -561,7 +561,7 @@ void test_status_worktree__interruptable_foreach(void)
 	git_repository *repo = cl_git_sandbox_init("status");
 
 	cl_assert_equal_i(
-		GIT_EUSER, git_status_foreach(repo, cb_status__interrupt, &count)
+		-111, git_status_foreach(repo, cb_status__interrupt, &count)
 	);
 
 	cl_assert_equal_i(8, count);
diff --git a/tests/valgrind-supp-mac.txt b/tests/valgrind-supp-mac.txt
index 99833d091..0cdc975fa 100644
--- a/tests/valgrind-supp-mac.txt
+++ b/tests/valgrind-supp-mac.txt
@@ -103,14 +103,6 @@
 	fun:ssl23_connect
 }
 {
-	mac-ssl-uninitialized-4
-	Memcheck:Param
-	...
-	obj:/usr/lib/libcrypto.0.9.8.dylib
-	...
-	fun:ssl23_connect
-}
-{
 	mac-ssl-leak-1
 	Memcheck:Leak
 	...