Diff iterators

This refactors the diff output code so that an iterator object
can be used to traverse and generate the diffs, instead of just
the `foreach()` style with callbacks.  The code has been rearranged
so that the two styles can still share most functions.

This also replaces `GIT_REVWALKOVER` with `GIT_ITEROVER` and uses
that as a common error code for marking the end of iteration when
using a iterator style of object.

12 files changed, 809 insertions, 274 deletions

diff --git a/src/attr.c b/src/attr.c
index 993220667..68f8d7de6 100644
--- a/src/attr.c
+++ b/src/attr.c
@@ -188,6 +188,7 @@ int git_attr_foreach(
 
 				error = callback(assign->name, assign->value, payload);
 				if (error) {
+					giterr_clear();
 					error = GIT_EUSER;
 					goto cleanup;
 				}
diff --git a/src/config_file.c b/src/config_file.c
index d3fb56aaa..c575649af 100644
--- a/src/config_file.c
+++ b/src/config_file.c
@@ -221,6 +221,7 @@ static int file_foreach(
 
 			/* abort iterator on non-zero return value */
 			if (fn(key, var->value, data)) {
+				giterr_clear();
 				result = GIT_EUSER;
 				goto cleanup;
 			}
diff --git a/src/diff.c b/src/diff.c
index 430f52e0a..f8a01086c 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -316,6 +316,7 @@ static git_diff_list *git_diff_list_alloc(
 	if (diff == NULL)
 		return NULL;
 
+	GIT_REFCOUNT_INC(diff);
 	diff->repo = repo;
 
 	if (git_vector_init(&diff->deltas, 0, diff_delta__cmp) < 0 ||
@@ -391,15 +392,12 @@ fail:
 	return NULL;
 }
 
-void git_diff_list_free(git_diff_list *diff)
+static void diff_list_free(git_diff_list *diff)
 {
 	git_diff_delta *delta;
 	git_attr_fnmatch *match;
 	unsigned int i;
 
-	if (!diff)
-		return;
-
 	git_vector_foreach(&diff->deltas, i, delta) {
 		git__free(delta);
 		diff->deltas.contents[i] = NULL;
@@ -416,6 +414,14 @@ void git_diff_list_free(git_diff_list *diff)
 	git__free(diff);
 }
 
+void git_diff_list_free(git_diff_list *diff)
+{
+	if (!diff)
+		return;
+
+	GIT_REFCOUNT_DEC(diff, diff_list_free);
+}
+
 static int oid_for_workdir_item(
 	git_repository *repo,
 	const git_index_entry *item,
diff --git a/src/diff.h b/src/diff.h
index 6cc854fbd..2785fa425 100644
--- a/src/diff.h
+++ b/src/diff.h
@@ -26,6 +26,7 @@ enum {
 };
 
 struct git_diff_list {
+	git_refcount     rc;
 	git_repository   *repo;
 	git_diff_options opts;
 	git_vector       pathspec;
diff --git a/src/diff_output.c b/src/diff_output.c
index 1f2c7233f..69921741c 100644
--- a/src/diff_output.c
+++ b/src/diff_output.c
@@ -16,16 +16,35 @@
 #include "fileops.h"
 #include "filter.h"
 
+/*
+ * A diff_delta_context represents all of the information that goes into
+ * processing the diff of an observed file change.  In the case of the
+ * git_diff_foreach() call it is an emphemeral structure that is filled
+ * in to execute each diff.  In the case of a git_diff_iterator, it holds
+ * most of the information for the diff in progress.
+ */
 typedef struct {
-	git_diff_list *diff;
-	void *cb_data;
-	git_diff_hunk_fn hunk_cb;
-	git_diff_data_fn line_cb;
-	unsigned int index;
+	git_repository   *repo;
+	git_diff_options *opts;
+	xdemitconf_t xdiff_config;
+	xpparam_t    xdiff_params;
 	git_diff_delta *delta;
+	uint32_t prepped  : 1;
+	uint32_t loaded   : 1;
+	uint32_t diffable : 1;
+	uint32_t diffed   : 1;
+	git_iterator_type_t old_src;
+	git_iterator_type_t new_src;
+	git_blob *old_blob;
+	git_blob *new_blob;
+	git_map   old_data;
+	git_map   new_data;
+	void *cb_data;
+	git_diff_hunk_fn per_hunk;
+	git_diff_data_fn per_line;
+	int cb_error;
 	git_diff_range range;
-	int error;
-} diff_output_info;
+} diff_delta_context;
 
 static int read_next_int(const char **str, int *value)
 {
@@ -41,71 +60,89 @@ static int read_next_int(const char **str, int *value)
 	return (digits > 0) ? 0 : -1;
 }
 
-static int diff_output_cb(void *priv, mmbuffer_t *bufs, int len)
+static int parse_hunk_header(git_diff_range *range, const char *header)
 {
-	diff_output_info *info = priv;
-
-	if (len == 1 && info->hunk_cb) {
-		git_diff_range range = { -1, 0, -1, 0 };
-		const char *scan = bufs[0].ptr;
+	/* expect something of the form "@@ -%d[,%d] +%d[,%d] @@" */
+	if (*header != '@')
+		return -1;
+	if (read_next_int(&header, &range->old_start) < 0)
+		return -1;
+	if (*header == ',') {
+		if (read_next_int(&header, &range->old_lines) < 0)
+			return -1;
+	} else
+		range->old_lines = 1;
+	if (read_next_int(&header, &range->new_start) < 0)
+		return -1;
+	if (*header == ',') {
+		if (read_next_int(&header, &range->new_lines) < 0)
+			return -1;
+	} else
+		range->new_lines = 1;
+	if (range->old_start < 0 || range->new_start < 0)
+		return -1;
 
-		/* expect something of the form "@@ -%d[,%d] +%d[,%d] @@" */
-		if (*scan != '@')
-			info->error = -1;
-		else if (read_next_int(&scan, &range.old_start) < 0)
-			info->error = -1;
-		else if (*scan == ',' && read_next_int(&scan, &range.old_lines) < 0)
-			info->error = -1;
-		else if (read_next_int(&scan, &range.new_start) < 0)
-			info->error = -1;
-		else if (*scan == ',' && read_next_int(&scan, &range.new_lines) < 0)
-			info->error = -1;
-		else if (range.old_start < 0 || range.new_start < 0)
-			info->error = -1;
-		else {
-			memcpy(&info->range, &range, sizeof(git_diff_range));
+	return 0;
+}
 
-			if (info->hunk_cb(
-					info->cb_data, info->delta, &range, bufs[0].ptr, bufs[0].size))
-				info->error = GIT_EUSER;
-		}
+static int format_hunk_header(char *header, size_t len, git_diff_range *range)
+{
+	if (range->old_lines != 1) {
+		if (range->new_lines != 1)
+			return snprintf(
+				header, len, "@@ -%d,%d +%d,%d @@",
+				range->old_start, range->old_lines,
+				range->new_start, range->new_lines);
+		else
+			return snprintf(
+				header, len, "@@ -%d,%d +%d @@",
+				range->old_start, range->old_lines, range->new_start);
+	} else {
+		if (range->new_lines != 1)
+			return snprintf(
+				header, len, "@@ -%d +%d,%d @@",
+				range->old_start, range->new_start, range->new_lines);
+		else
+			return snprintf(
+				header, len, "@@ -%d +%d @@",
+				range->old_start, range->new_start);
 	}
+}
 
-	if ((len == 2 || len == 3) && info->line_cb) {
-		int origin;
-
-		/* expect " "/"-"/"+", then data, then maybe newline */
-		origin =
-			(*bufs[0].ptr == '+') ? GIT_DIFF_LINE_ADDITION :
-			(*bufs[0].ptr == '-') ? GIT_DIFF_LINE_DELETION :
-			GIT_DIFF_LINE_CONTEXT;
+static bool diff_delta_is_ambiguous(git_diff_delta *delta)
+{
+	return (git_oid_iszero(&delta->new_file.oid) &&
+			(delta->new_file.flags & GIT_DIFF_FILE_VALID_OID) == 0 &&
+			delta->status == GIT_DELTA_MODIFIED);
+}
 
-		if (info->line_cb(
-				info->cb_data, info->delta, &info->range, origin, bufs[1].ptr, bufs[1].size))
-			info->error = GIT_EUSER;
+static bool diff_delta_should_skip(git_diff_options *opts, git_diff_delta *delta)
+{
+	if (delta->status == GIT_DELTA_UNMODIFIED &&
+		(opts->flags & GIT_DIFF_INCLUDE_UNMODIFIED) == 0)
+		return true;
 
-		/* This should only happen if we are adding a line that does not
-		 * have a newline at the end and the old code did.  In that case,
-		 * we have a ADD with a DEL_EOFNL as a pair.
-		 */
-		else if (len == 3) {
-			origin = (origin == GIT_DIFF_LINE_ADDITION) ?
-				GIT_DIFF_LINE_DEL_EOFNL : GIT_DIFF_LINE_ADD_EOFNL;
+	if (delta->status == GIT_DELTA_IGNORED &&
+		(opts->flags & GIT_DIFF_INCLUDE_IGNORED) == 0)
+		return true;
 
-			if (info->line_cb(
-					info->cb_data, info->delta, &info->range, origin, bufs[2].ptr, bufs[2].size))
-				info->error = GIT_EUSER;
-		}
-	}
+	if (delta->status == GIT_DELTA_UNTRACKED &&
+		(opts->flags & GIT_DIFF_INCLUDE_UNTRACKED) == 0)
+		return true;
 
-	return info->error;
+	return false;
 }
 
 #define BINARY_DIFF_FLAGS (GIT_DIFF_FILE_BINARY|GIT_DIFF_FILE_NOT_BINARY)
 
-static int update_file_is_binary_by_attr(git_repository *repo, git_diff_file *file)
+static int update_file_is_binary_by_attr(
+	git_repository *repo, git_diff_file *file)
 {
 	const char *value;
+
+	if (!repo)
+		return 0;
+
 	if (git_attr_get(&value, repo, 0, file->path, "diff") < 0)
 		return -1;
 
@@ -129,11 +166,10 @@ static void update_delta_is_binary(git_diff_delta *delta)
 	/* otherwise leave delta->binary value untouched */
 }
 
-static int file_is_binary_by_attr(
-	git_diff_list *diff,
-	git_diff_delta *delta)
+static int diff_delta_is_binary_by_attr(diff_delta_context *ctxt)
 {
 	int error = 0, mirror_new;
+	git_diff_delta *delta = ctxt->delta;
 
 	delta->binary = -1;
 
@@ -148,7 +184,7 @@ static int file_is_binary_by_attr(
 	}
 
 	/* check if user is forcing us to text diff these files */
-	if (diff->opts.flags & GIT_DIFF_FORCE_TEXT) {
+	if (ctxt->opts->flags & GIT_DIFF_FORCE_TEXT) {
 		delta->old_file.flags |= GIT_DIFF_FILE_NOT_BINARY;
 		delta->new_file.flags |= GIT_DIFF_FILE_NOT_BINARY;
 		delta->binary = 0;
@@ -156,7 +192,7 @@ static int file_is_binary_by_attr(
 	}
 
 	/* check diff attribute +, -, or 0 */
-	if (update_file_is_binary_by_attr(diff->repo, &delta->old_file) < 0)
+	if (update_file_is_binary_by_attr(ctxt->repo, &delta->old_file) < 0)
 		return -1;
 
 	mirror_new = (delta->new_file.path == delta->old_file.path ||
@@ -164,23 +200,21 @@ static int file_is_binary_by_attr(
 	if (mirror_new)
 		delta->new_file.flags |= (delta->old_file.flags & BINARY_DIFF_FLAGS);
 	else
-		error = update_file_is_binary_by_attr(diff->repo, &delta->new_file);
+		error = update_file_is_binary_by_attr(ctxt->repo, &delta->new_file);
 
 	update_delta_is_binary(delta);
 
 	return error;
 }
 
-static int file_is_binary_by_content(
-	git_diff_delta *delta,
-	git_map *old_data,
-	git_map *new_data)
+static int diff_delta_is_binary_by_content(diff_delta_context *ctxt)
 {
+	git_diff_delta *delta = ctxt->delta;
 	git_buf search;
 
 	if ((delta->old_file.flags & BINARY_DIFF_FLAGS) == 0) {
-		search.ptr  = old_data->data;
-		search.size = min(old_data->len, 4000);
+		search.ptr  = ctxt->old_data.data;
+		search.size = min(ctxt->old_data.len, 4000);
 
 		if (git_buf_is_binary(&search))
 			delta->old_file.flags |= GIT_DIFF_FILE_BINARY;
@@ -189,8 +223,8 @@ static int file_is_binary_by_content(
 	}
 
 	if ((delta->new_file.flags & BINARY_DIFF_FLAGS) == 0) {
-		search.ptr  = new_data->data;
-		search.size = min(new_data->len, 4000);
+		search.ptr  = ctxt->new_data.data;
+		search.size = min(ctxt->new_data.len, 4000);
 
 		if (git_buf_is_binary(&search))
 			delta->new_file.flags |= GIT_DIFF_FILE_BINARY;
@@ -256,16 +290,21 @@ static int get_workdir_content(
 		return -1;
 
 	if (S_ISLNK(file->mode)) {
-		ssize_t read_len;
+		ssize_t alloc_len, read_len;
 
 		file->flags |= GIT_DIFF_FILE_FREE_DATA;
 		file->flags |= GIT_DIFF_FILE_BINARY;
 
-		map->data = git__malloc((size_t)file->size + 1);
+		/* link path on disk could be UTF-16, so prepare a buffer that is
+		 * big enough to handle some UTF-8 data expansion
+		 */
+		alloc_len = (ssize_t)(file->size * 2) + 1;
+
+		map->data = git__malloc(alloc_len);
 		GITERR_CHECK_ALLOC(map->data);
 
-		read_len = p_readlink(path.ptr, map->data, (size_t)file->size + 1);
-		if (read_len != (ssize_t)file->size) {
+		read_len = p_readlink(path.ptr, map->data, (int)alloc_len);
+		if (read_len < 0) {
 			giterr_set(GITERR_OS, "Failed to read symlink '%s'", file->path);
 			error = -1;
 		} else
@@ -286,189 +325,304 @@ static void release_content(git_diff_file *file, git_map *map, git_blob *blob)
 
 	if (file->flags & GIT_DIFF_FILE_FREE_DATA) {
 		git__free(map->data);
-		map->data = NULL;
+		map->data = "";
+		map->len  = 0;
 		file->flags &= ~GIT_DIFF_FILE_FREE_DATA;
 	}
 	else if (file->flags & GIT_DIFF_FILE_UNMAP_DATA) {
 		git_futils_mmap_free(map);
-		map->data = NULL;
+		map->data = "";
+		map->len  = 0;
 		file->flags &= ~GIT_DIFF_FILE_UNMAP_DATA;
 	}
 }
 
-static void fill_map_from_mmfile(git_map *dst, mmfile_t *src) {
-	assert(dst && src);
+static void diff_delta_init_context(
+	diff_delta_context *ctxt,
+	git_repository   *repo,
+	git_diff_options *opts,
+	git_iterator_type_t old_src,
+	git_iterator_type_t new_src)
+{
+	memset(ctxt, 0, sizeof(diff_delta_context));
+
+	ctxt->repo = repo;
+	ctxt->opts = opts;
+	ctxt->old_src = old_src;
+	ctxt->new_src = new_src;
 
-	dst->data = src->ptr;
-	dst->len = src->size;
-#ifdef GIT_WIN32
-	dst->fmh = NULL;
-#endif
+	setup_xdiff_options(opts, &ctxt->xdiff_config, &ctxt->xdiff_params);
 }
 
-int git_diff_foreach(
-	git_diff_list *diff,
-	void *data,
-	git_diff_file_fn file_cb,
-	git_diff_hunk_fn hunk_cb,
-	git_diff_data_fn line_cb)
+static void diff_delta_init_context_from_diff_list(
+	diff_delta_context *ctxt,
+	git_diff_list *diff)
 {
-	int error = 0;
-	diff_output_info info;
-	git_diff_delta *delta;
-	xpparam_t    xdiff_params;
-	xdemitconf_t xdiff_config;
-	xdemitcb_t   xdiff_callback;
+	diff_delta_init_context(
+		ctxt, diff->repo, &diff->opts, diff->old_src, diff->new_src);
+}
 
-	memset(&info, 0, sizeof(info));
-	info.diff    = diff;
-	info.cb_data = data;
-	info.hunk_cb = hunk_cb;
-	info.line_cb = line_cb;
+static void diff_delta_unload(diff_delta_context *ctxt)
+{
+	ctxt->diffed = 0;
 
-	setup_xdiff_options(&diff->opts, &xdiff_config, &xdiff_params);
-	memset(&xdiff_callback, 0, sizeof(xdiff_callback));
-	xdiff_callback.outf = diff_output_cb;
-	xdiff_callback.priv = &info;
+	if (ctxt->loaded) {
+		release_content(&ctxt->delta->old_file, &ctxt->old_data, ctxt->old_blob);
+		release_content(&ctxt->delta->new_file, &ctxt->new_data, ctxt->new_blob);
+		ctxt->loaded = 0;
+	}
 
-	git_vector_foreach(&diff->deltas, info.index, delta) {
-		git_blob *old_blob = NULL, *new_blob = NULL;
-		git_map old_data, new_data;
-		mmfile_t old_xdiff_data, new_xdiff_data;
+	ctxt->delta = NULL;
+	ctxt->prepped = 0;
+}
 
-		if (delta->status == GIT_DELTA_UNMODIFIED &&
-			(diff->opts.flags & GIT_DIFF_INCLUDE_UNMODIFIED) == 0)
-			continue;
+static int diff_delta_prep(diff_delta_context *ctxt)
+{
+	int error;
 
-		if (delta->status == GIT_DELTA_IGNORED &&
-			(diff->opts.flags & GIT_DIFF_INCLUDE_IGNORED) == 0)
-			continue;
+	if (ctxt->prepped || !ctxt->delta)
+		return 0;
 
-		if (delta->status == GIT_DELTA_UNTRACKED &&
-			(diff->opts.flags & GIT_DIFF_INCLUDE_UNTRACKED) == 0)
-			continue;
+	error = diff_delta_is_binary_by_attr(ctxt);
 
-		if ((error = file_is_binary_by_attr(diff, delta)) < 0)
-			goto cleanup;
+	ctxt->prepped = !error;
 
-		old_data.data = "";
-		old_data.len = 0;
-		new_data.data = "";
-		new_data.len  = 0;
+	return error;
+}
 
-		/* TODO: Partial blob reading to defer loading whole blob.
-		 * I.e. I want a blob with just the first 4kb loaded, then
-		 * later on I will read the rest of the blob if needed.
-		 */
+static int diff_delta_load(diff_delta_context *ctxt)
+{
+	int error = 0;
+	git_diff_delta *delta = ctxt->delta;
 
-		/* map files */
-		if (delta->binary != 1 &&
-			(hunk_cb || line_cb || git_oid_iszero(&delta->old_file.oid)) &&
-			(delta->status == GIT_DELTA_DELETED ||
-			 delta->status == GIT_DELTA_MODIFIED))
-		{
-			if (diff->old_src == GIT_ITERATOR_WORKDIR)
-				error = get_workdir_content(diff->repo, &delta->old_file, &old_data);
-			else
-				error = get_blob_content(
-					diff->repo, &delta->old_file.oid, &old_data, &old_blob);
+	if (ctxt->loaded || !ctxt->delta)
+		return 0;
 
-			if (error < 0)
-				goto cleanup;
+	if (!ctxt->prepped && (error = diff_delta_prep(ctxt)) < 0)
+		goto cleanup;
+
+	ctxt->old_data.data = "";
+	ctxt->old_data.len  = 0;
+	ctxt->old_blob      = NULL;
+
+	if (!error && delta->binary != 1 &&
+		(delta->status == GIT_DELTA_DELETED ||
+		 delta->status == GIT_DELTA_MODIFIED))
+	{
+		if (ctxt->old_src == GIT_ITERATOR_WORKDIR)
+			error = get_workdir_content(
+				ctxt->repo, &delta->old_file, &ctxt->old_data);
+		else {
+			error = get_blob_content(
+				ctxt->repo, &delta->old_file.oid,
+				&ctxt->old_data, &ctxt->old_blob);
+
+			if (ctxt->new_src == GIT_ITERATOR_WORKDIR) {
+				/* TODO: convert crlf of blob content */
+			}
 		}
+	}
 
-		if (delta->binary != 1 &&
-			(hunk_cb || line_cb || git_oid_iszero(&delta->new_file.oid)) &&
-			(delta->status == GIT_DELTA_ADDED ||
-			 delta->status == GIT_DELTA_MODIFIED))
-		{
-			if (diff->new_src == GIT_ITERATOR_WORKDIR)
-				error = get_workdir_content(diff->repo, &delta->new_file, &new_data);
-			else
-				error = get_blob_content(
-					diff->repo, &delta->new_file.oid, &new_data, &new_blob);
+	ctxt->new_data.data = "";
+	ctxt->new_data.len  = 0;
+	ctxt->new_blob      = NULL;
+
+	if (!error && delta->binary != 1 &&
+		(delta->status == GIT_DELTA_ADDED ||
+		 delta->status == GIT_DELTA_MODIFIED))
+	{
+		if (ctxt->new_src == GIT_ITERATOR_WORKDIR)
+			error = get_workdir_content(
+				ctxt->repo, &delta->new_file, &ctxt->new_data);
+		else {
+			error = get_blob_content(
+				ctxt->repo, &delta->new_file.oid,
+				&ctxt->new_data, &ctxt->new_blob);
 
+			if (ctxt->old_src == GIT_ITERATOR_WORKDIR) {
+				/* TODO: convert crlf of blob content */
+			}
+		}
+
+		if (!error && !(delta->new_file.flags & GIT_DIFF_FILE_VALID_OID)) {
+			error = git_odb_hash(
+				&delta->new_file.oid, ctxt->new_data.data,
+				ctxt->new_data.len, GIT_OBJ_BLOB);
 			if (error < 0)
 				goto cleanup;
 
-			if ((delta->new_file.flags & GIT_DIFF_FILE_VALID_OID) == 0) {
-				error = git_odb_hash(
-					&delta->new_file.oid, new_data.data, new_data.len, GIT_OBJ_BLOB);
+			delta->new_file.flags |= GIT_DIFF_FILE_VALID_OID;
 
-				if (error < 0)
+			/* since we did not have the definitive oid, we may have
+			 * incorrect status and need to skip this item.
+			 */
+			if (delta->old_file.mode == delta->new_file.mode &&
+				!git_oid_cmp(&delta->old_file.oid, &delta->new_file.oid))
+			{
+				delta->status = GIT_DELTA_UNMODIFIED;
+
+				if ((ctxt->opts->flags & GIT_DIFF_INCLUDE_UNMODIFIED) == 0)
 					goto cleanup;
-				delta->new_file.flags |= GIT_DIFF_FILE_VALID_OID;
-
-				/* since we did not have the definitive oid, we may have
-				 * incorrect status and need to skip this item.
-				 */
-				if (delta->old_file.mode == delta->new_file.mode &&
-					!git_oid_cmp(&delta->old_file.oid, &delta->new_file.oid))
-				{
-					delta->status = GIT_DELTA_UNMODIFIED;
-					if ((diff->opts.flags & GIT_DIFF_INCLUDE_UNMODIFIED) == 0)
-						goto cleanup;
-				}
 			}
 		}
+	}
+
+	/* if we have not already decided whether file is binary,
+	 * check the first 4K for nul bytes to decide...
+	 */
+	if (!error && delta->binary == -1)
+		error = diff_delta_is_binary_by_content(ctxt);
+
+cleanup:
+	ctxt->loaded = !error;
+
+	/* flag if we would want to diff the contents of these files */
+	if (ctxt->loaded)
+		ctxt->diffable =
+			(delta->binary != 1 &&
+			 delta->status != GIT_DELTA_UNMODIFIED &&
+			 (ctxt->old_data.len || ctxt->new_data.len) &&
+			 git_oid_cmp(&delta->old_file.oid, &delta->new_file.oid));
+
+	return error;
+}
+
+static int diff_delta_cb(void *priv, mmbuffer_t *bufs, int len)
+{
+	diff_delta_context *ctxt = priv;
+
+	if (len == 1) {
+		if ((ctxt->cb_error = parse_hunk_header(&ctxt->range, bufs[0].ptr)) < 0)
+			return ctxt->cb_error;
+
+		if (ctxt->per_hunk != NULL &&
+			ctxt->per_hunk(ctxt->cb_data, ctxt->delta, &ctxt->range,
+				bufs[0].ptr, bufs[0].size))
+			ctxt->cb_error = GIT_EUSER;
+	}
 
-		/* if we have not already decided whether file is binary,
-		 * check the first 4K for nul bytes to decide...
+	if (len == 2 || len == 3) {
+		/* expect " "/"-"/"+", then data */
+		char origin =
+			(*bufs[0].ptr == '+') ? GIT_DIFF_LINE_ADDITION :
+			(*bufs[0].ptr == '-') ? GIT_DIFF_LINE_DELETION :
+			GIT_DIFF_LINE_CONTEXT;
+
+		if (ctxt->per_line != NULL &&
+			ctxt->per_line(ctxt->cb_data, ctxt->delta, &ctxt->range, origin,
+				bufs[1].ptr, bufs[1].size))
+			ctxt->cb_error = GIT_EUSER;
+	}
+
+	if (len == 3 && !ctxt->cb_error) {
+		/* This should only happen if we are adding a line that does not
+		 * have a newline at the end and the old code did.  In that case,
+		 * we have a ADD with a DEL_EOFNL as a pair.
 		 */
-		if (delta->binary == -1) {
-			error = file_is_binary_by_content(
-				delta, &old_data, &new_data);
-			if (error < 0)
+		char origin =
+			(*bufs[0].ptr == '+') ? GIT_DIFF_LINE_DEL_EOFNL :
+			(*bufs[0].ptr == '-') ? GIT_DIFF_LINE_ADD_EOFNL :
+			GIT_DIFF_LINE_CONTEXT;
+
+		if (ctxt->per_line != NULL &&
+			ctxt->per_line(ctxt->cb_data, ctxt->delta, &ctxt->range, origin,
+				bufs[2].ptr, bufs[2].size))
+			ctxt->cb_error = GIT_EUSER;
+	}
+
+	return ctxt->cb_error;
+}
+
+static int diff_delta_exec(
+	diff_delta_context *ctxt,
+	void *cb_data,
+	git_diff_hunk_fn per_hunk,
+	git_diff_data_fn per_line)
+{
+	int error = 0;
+	xdemitcb_t xdiff_callback;
+	mmfile_t old_xdiff_data, new_xdiff_data;
+
+	if (ctxt->diffed || !ctxt->delta)
+		return 0;
+
+	if (!ctxt->loaded && (error = diff_delta_load(ctxt)) < 0)
+		goto cleanup;
+
+	if (!ctxt->diffable)
+		return 0;
+
+	ctxt->cb_data  = cb_data;
+	ctxt->per_hunk = per_hunk;
+	ctxt->per_line = per_line;
+	ctxt->cb_error = 0;
+
+	memset(&xdiff_callback, 0, sizeof(xdiff_callback));
+	xdiff_callback.outf = diff_delta_cb;
+	xdiff_callback.priv = ctxt;
+
+	old_xdiff_data.ptr  = ctxt->old_data.data;
+	old_xdiff_data.size = ctxt->old_data.len;
+	new_xdiff_data.ptr  = ctxt->new_data.data;
+	new_xdiff_data.size = ctxt->new_data.len;
+
+	xdl_diff(&old_xdiff_data, &new_xdiff_data,
+		&ctxt->xdiff_params, &ctxt->xdiff_config, &xdiff_callback);
+
+	error = ctxt->cb_error;
+
+cleanup:
+	ctxt->diffed = !error;
+
+	return error;
+}
+
+int git_diff_foreach(
+	git_diff_list *diff,
+	void *data,
+	git_diff_file_fn file_cb,
+	git_diff_hunk_fn hunk_cb,
+	git_diff_data_fn line_cb)
+{
+	int error = 0;
+	diff_delta_context ctxt;
+	size_t idx;
+
+	diff_delta_init_context_from_diff_list(&ctxt, diff);
+
+	git_vector_foreach(&diff->deltas, idx, ctxt.delta) {
+		if (diff_delta_is_ambiguous(ctxt.delta))
+			if ((error = diff_delta_load(&ctxt)) < 0)
 				goto cleanup;
-		}
 
-		/* TODO: if ignore_whitespace is set, then we *must* do text
-		 * diffs to tell if a file has really been changed.
-		 */
+		if (diff_delta_should_skip(ctxt.opts, ctxt.delta))
+			continue;
+
+		if ((error = diff_delta_load(&ctxt)) < 0)
+			goto cleanup;
 
 		if (file_cb != NULL &&
-			file_cb(data, delta, (float)info.index / diff->deltas.length))
+			file_cb(data, ctxt.delta, (float)idx / diff->deltas.length) != 0)
 		{
 			error = GIT_EUSER;
 			goto cleanup;
 		}
 
-		/* don't do hunk and line diffs if file is binary */
-		if (delta->binary == 1)
-			goto cleanup;
-
-		/* nothing to do if we did not get data */
-		if (!old_data.len && !new_data.len)
-			goto cleanup;
-
-		/* nothing to do if only diff was a mode change */
-		if (!git_oid_cmp(&delta->old_file.oid, &delta->new_file.oid))
-			goto cleanup;
-
-		assert(hunk_cb || line_cb);
-
-		info.delta = delta;
-		old_xdiff_data.ptr = old_data.data;
-		old_xdiff_data.size = old_data.len;
-		new_xdiff_data.ptr = new_data.data;
-		new_xdiff_data.size = new_data.len;
-
-		xdl_diff(&old_xdiff_data, &new_xdiff_data,
-			&xdiff_params, &xdiff_config, &xdiff_callback);
-		error = info.error;
+		error = diff_delta_exec(&ctxt, data, hunk_cb, line_cb);
 
 cleanup:
-		release_content(&delta->old_file, &old_data, old_blob);
-		release_content(&delta->new_file, &new_data, new_blob);
+		diff_delta_unload(&ctxt);
 
 		if (error < 0)
 			break;
 	}
 
+	if (error == GIT_EUSER)
+		giterr_clear();
+
 	return error;
 }
 
-
 typedef struct {
 	git_diff_list *diff;
 	git_diff_data_fn print_cb;
@@ -531,7 +685,10 @@ static int print_compact(void *data, git_diff_delta *delta, float progress)
 
 	if (pi->print_cb(pi->cb_data, delta, NULL, GIT_DIFF_LINE_FILE_HDR,
 			git_buf_cstr(pi->buf), git_buf_len(pi->buf)))
+	{
+		giterr_clear();
 		return GIT_EUSER;
+	}
 
 	return 0;
 }
@@ -628,7 +785,10 @@ static int print_patch_file(void *data, git_diff_delta *delta, float progress)
 		return -1;
 
     if (pi->print_cb(pi->cb_data, delta, NULL, GIT_DIFF_LINE_FILE_HDR, git_buf_cstr(pi->buf), git_buf_len(pi->buf)))
+	{
+		giterr_clear();
 		return GIT_EUSER;
+	}
 
     if (delta->binary != 1)
         return 0;
@@ -642,7 +802,10 @@ static int print_patch_file(void *data, git_diff_delta *delta, float progress)
 
 	if (pi->print_cb(pi->cb_data, delta, NULL, GIT_DIFF_LINE_BINARY,
 			git_buf_cstr(pi->buf), git_buf_len(pi->buf)))
+	{
+		giterr_clear();
 		return GIT_EUSER;
+	}
 
 	return 0;
 }
@@ -662,7 +825,10 @@ static int print_patch_hunk(
 
 	if (pi->print_cb(pi->cb_data, d, r, GIT_DIFF_LINE_HUNK_HDR,
 			git_buf_cstr(pi->buf), git_buf_len(pi->buf)))
+	{
+		giterr_clear();
 		return GIT_EUSER;
+	}
 
 	return 0;
 }
@@ -691,7 +857,10 @@ static int print_patch_line(
 
 	if (pi->print_cb(pi->cb_data, delta, range, line_origin,
 			git_buf_cstr(pi->buf), git_buf_len(pi->buf)))
+	{
+		giterr_clear();
 		return GIT_EUSER;
+	}
 
 	return 0;
 }
@@ -726,17 +895,36 @@ int git_diff_entrycount(git_diff_list *diff, int delta_t)
 
 	assert(diff);
 
-	if (delta_t < 0)
-		return (int)diff->deltas.length;
-
 	git_vector_foreach(&diff->deltas, i, delta) {
-		if (delta->status == (git_delta_t)delta_t)
+		if (diff_delta_should_skip(&diff->opts, delta))
+			continue;
+
+		if (delta_t < 0 || delta->status == (git_delta_t)delta_t)
 			count++;
 	}
 
+	/* It is possible that this has overcounted the number of diffs because
+	 * there may be entries that are marked as MODIFIED due to differences
+	 * in stat() output that will turn out to be the same once we calculate
+	 * the actual SHA of the data on disk.
+	 */
+
 	return count;
 }
 
+static void set_data_from_blob(
+	git_blob *blob, git_map *map, git_diff_file *file)
+{
+	if (blob) {
+		map->data = (char *)git_blob_rawcontent(blob);
+		file->size = map->len = git_blob_rawsize(blob);
+		git_oid_cpy(&file->oid, git_object_id((const git_object *)blob));
+	} else {
+		map->data = "";
+		file->size = map->len = 0;
+	}
+}
+
 int git_diff_blobs(
 	git_blob *old_blob,
 	git_blob *new_blob,
@@ -746,17 +934,11 @@ int git_diff_blobs(
 	git_diff_hunk_fn hunk_cb,
 	git_diff_data_fn line_cb)
 {
-	diff_output_info info;
+	int error;
+	diff_delta_context ctxt;
 	git_diff_delta delta;
-	mmfile_t old_data, new_data;
-	git_map old_map, new_map;
-	xpparam_t xdiff_params;
-	xdemitconf_t xdiff_config;
-	xdemitcb_t xdiff_callback;
 	git_blob *new, *old;
 
-	memset(&delta, 0, sizeof(delta));
-
 	new = new_blob;
 	old = old_blob;
 
@@ -766,25 +948,16 @@ int git_diff_blobs(
 		new = swap;
 	}
 
-	if (old) {
-		old_data.ptr  = (char *)git_blob_rawcontent(old);
-		old_data.size = git_blob_rawsize(old);
-		git_oid_cpy(&delta.old_file.oid, git_object_id((const git_object *)old));
-	} else {
-		old_data.ptr  = "";
-		old_data.size = 0;
-	}
-
-	if (new) {
-		new_data.ptr  = (char *)git_blob_rawcontent(new);
-		new_data.size = git_blob_rawsize(new);
-		git_oid_cpy(&delta.new_file.oid, git_object_id((const git_object *)new));
-	} else {
-		new_data.ptr  = "";
-		new_data.size = 0;
-	}
+	diff_delta_init_context(
+		&ctxt, NULL, options, GIT_ITERATOR_TREE, GIT_ITERATOR_TREE);
 
 	/* populate a "fake" delta record */
+
+	memset(&delta, 0, sizeof(delta));
+
+	set_data_from_blob(old, &ctxt.old_data, &delta.old_file);
+	set_data_from_blob(new, &ctxt.new_data, &delta.new_file);
+
 	delta.status = new ?
 		(old ? GIT_DELTA_MODIFIED : GIT_DELTA_ADDED) :
 		(old ? GIT_DELTA_DELETED : GIT_DELTA_UNTRACKED);
@@ -792,39 +965,370 @@ int git_diff_blobs(
 	if (git_oid_cmp(&delta.new_file.oid, &delta.old_file.oid) == 0)
 		delta.status = GIT_DELTA_UNMODIFIED;
 
-	delta.old_file.size = old_data.size;
-	delta.new_file.size = new_data.size;
+	ctxt.delta = &delta;
+
+	if ((error = diff_delta_prep(&ctxt)) < 0)
+		goto cleanup;
+
+	if (delta.binary == -1 &&
+		(error = diff_delta_is_binary_by_content(&ctxt)) < 0)
+		goto cleanup;
+
+	ctxt.loaded = 1;
+	ctxt.diffable = (delta.binary != 1 && delta.status != GIT_DELTA_UNMODIFIED);
+
+	/* do diffs */
+
+	if (file_cb != NULL && file_cb(cb_data, &delta, 1)) {
+		error = GIT_EUSER;
+		goto cleanup;
+	}
+
+	error = diff_delta_exec(&ctxt, cb_data, hunk_cb, line_cb);
+
+cleanup:
+	if (error == GIT_EUSER)
+		giterr_clear();
+
+	diff_delta_unload(&ctxt);
+
+	return error;
+}
+
+typedef struct diffiter_line diffiter_line;
+struct diffiter_line {
+	diffiter_line *next;
+	char origin;
+	const char *ptr;
+	size_t len;
+};
+
+typedef struct diffiter_hunk diffiter_hunk;
+struct diffiter_hunk {
+	diffiter_hunk *next;
+	git_diff_range range;
+	diffiter_line *line_head;
+	size_t line_count;
+};
+
+struct git_diff_iterator {
+	git_diff_list *diff;
+	diff_delta_context ctxt;
+	size_t file_index;
+	size_t next_index;
+	size_t file_count;
+	git_pool hunks;
+	size_t   hunk_count;
+	diffiter_hunk *hunk_head;
+	diffiter_hunk *hunk_curr;
+	char hunk_header[128];
+	git_pool lines;
+	size_t   line_count;
+	diffiter_line *line_curr;
+};
+
+typedef struct {
+	git_diff_iterator *iter;
+	diffiter_hunk *last_hunk;
+	diffiter_line *last_line;
+} diffiter_cb_info;
 
-	fill_map_from_mmfile(&old_map, &old_data);
-	fill_map_from_mmfile(&new_map, &new_data);
+static int diffiter_hunk_cb(
+	void *cb_data,
+	git_diff_delta *delta,
+	git_diff_range *range,
+	const char *header,
+	size_t header_len)
+{
+	diffiter_cb_info *info = cb_data;
+	git_diff_iterator *iter = info->iter;
+	diffiter_hunk *hunk;
+
+	GIT_UNUSED(delta);
+	GIT_UNUSED(header);
+	GIT_UNUSED(header_len);
 
-	if (file_is_binary_by_content(&delta, &old_map, &new_map) < 0)
+	if ((hunk = git_pool_mallocz(&iter->hunks, 1)) == NULL) {
+		iter->ctxt.cb_error = -1;
 		return -1;
+	}
 
-	if (file_cb != NULL && file_cb(cb_data, &delta, 1))
-		return GIT_EUSER;
+	if (info->last_hunk)
+		info->last_hunk->next = hunk;
+	info->last_hunk = hunk;
 
-	/* don't do hunk and line diffs if the two blobs are identical */
-	if (delta.status == GIT_DELTA_UNMODIFIED)
-		return 0;
+	memcpy(&hunk->range, range, sizeof(hunk->range));
+
+	iter->hunk_count++;
+
+	if (iter->hunk_head == NULL)
+		iter->hunk_curr = iter->hunk_head = hunk;
+
+	return 0;
+}
 
-	/* don't do hunk and line diffs if file is binary */
-	if (delta.binary == 1)
+static int diffiter_line_cb(
+	void *cb_data,
+	git_diff_delta *delta,
+	git_diff_range *range,
+	char line_origin,
+	const char *content,
+	size_t content_len)
+{
+	diffiter_cb_info *info = cb_data;
+	git_diff_iterator *iter = info->iter;
+	diffiter_line *line;
+
+	GIT_UNUSED(delta);
+	GIT_UNUSED(range);
+
+	if ((line = git_pool_mallocz(&iter->lines, 1)) == NULL) {
+		iter->ctxt.cb_error = -1;
+		return -1;
+	}
+
+	if (info->last_line)
+		info->last_line->next = line;
+	info->last_line = line;
+
+	line->origin = line_origin;
+	line->ptr = content;
+	line->len = content_len;
+
+	info->last_hunk->line_count++;
+	iter->line_count++;
+
+	if (info->last_hunk->line_head == NULL)
+		info->last_hunk->line_head = line;
+
+	return 0;
+}
+
+static int diffiter_do_diff_file(git_diff_iterator *iter)
+{
+	int error;
+	diffiter_cb_info info;
+
+	if (iter->ctxt.diffed || !iter->ctxt.delta)
 		return 0;
 
 	memset(&info, 0, sizeof(info));
-	info.diff    = NULL;
-	info.delta   = &delta;
-	info.cb_data = cb_data;
-	info.hunk_cb = hunk_cb;
-	info.line_cb = line_cb;
+	info.iter = iter;
 
-	setup_xdiff_options(options, &xdiff_config, &xdiff_params);
-	memset(&xdiff_callback, 0, sizeof(xdiff_callback));
-	xdiff_callback.outf = diff_output_cb;
-	xdiff_callback.priv = &info;
+	error = diff_delta_exec(
+		&iter->ctxt, &info, diffiter_hunk_cb, diffiter_line_cb);
+
+	if (error == GIT_EUSER)
+		error = iter->ctxt.cb_error;
+
+	return error;
+}
 
-	xdl_diff(&old_data, &new_data, &xdiff_params, &xdiff_config, &xdiff_callback);
+static void diffiter_do_unload_file(git_diff_iterator *iter)
+{
+	if (iter->ctxt.loaded) {
+		diff_delta_unload(&iter->ctxt);
+
+		git_pool_clear(&iter->lines);
+		git_pool_clear(&iter->hunks);
+	}
+
+	iter->ctxt.delta = NULL;
+	iter->hunk_head = NULL;
+	iter->hunk_count = 0;
+	iter->line_count = 0;
+}
+
+int git_diff_iterator_new(
+	git_diff_iterator **iterator_ptr,
+	git_diff_list *diff)
+{
+	size_t i;
+	git_diff_delta *delta;
+	git_diff_iterator *iter;
+
+	assert(diff && iterator_ptr);
+
+	*iterator_ptr = NULL;
+
+	iter = git__malloc(sizeof(git_diff_iterator));
+	GITERR_CHECK_ALLOC(iter);
+
+	memset(iter, 0, sizeof(*iter));
+
+	iter->diff = diff;
+	GIT_REFCOUNT_INC(iter->diff);
+
+	diff_delta_init_context_from_diff_list(&iter->ctxt, diff);
+
+	if (git_pool_init(&iter->hunks, sizeof(diffiter_hunk), 0) < 0 ||
+		git_pool_init(&iter->lines, sizeof(diffiter_line), 0) < 0)
+		goto fail;
+
+	git_vector_foreach(&diff->deltas, i, delta) {
+		if (diff_delta_should_skip(iter->ctxt.opts, delta))
+			continue;
+		iter->file_count++;
+	}
+
+	*iterator_ptr = iter;
+
+	return 0;
+
+fail:
+	git_diff_iterator_free(iter);
+
+	return -1;
+}
+
+void git_diff_iterator_free(git_diff_iterator *iter)
+{
+	diffiter_do_unload_file(iter);
+	git_diff_list_free(iter->diff); /* decrement ref count */
+	git__free(iter);
+}
+
+int git_diff_iterator_num_files(git_diff_iterator *iter)
+{
+	return (int)iter->file_count;
+}
+
+int git_diff_iterator_num_hunks_in_file(git_diff_iterator *iter)
+{
+	int error = diffiter_do_diff_file(iter);
+	return (error != 0) ? error : (int)iter->hunk_count;
+}
+
+int git_diff_iterator_num_lines_in_hunk(git_diff_iterator *iter)
+{
+	int error = diffiter_do_diff_file(iter);
+	return (error != 0) ? error : (int)iter->line_count;
+}
+
+int git_diff_iterator_next_file(
+	git_diff_delta **delta_ptr,
+	git_diff_iterator *iter)
+{
+	int error = 0;
+
+	assert(iter);
+
+	iter->file_index = iter->next_index;
+
+	diffiter_do_unload_file(iter);
 
-	return info.error;
+	while (!error) {
+		iter->ctxt.delta = git_vector_get(&iter->diff->deltas, iter->file_index);
+		if (!iter->ctxt.delta) {
+			error = GIT_ITEROVER;
+			break;
+		}
+
+		if (diff_delta_is_ambiguous(iter->ctxt.delta) &&
+			(error = diff_delta_load(&iter->ctxt)) < 0)
+			break;
+
+		if (!diff_delta_should_skip(iter->ctxt.opts, iter->ctxt.delta))
+			break;
+
+		iter->file_index++;
+	}
+
+	if (!error) {
+		iter->next_index = iter->file_index + 1;
+
+		error = diff_delta_prep(&iter->ctxt);
+	}
+
+	if (iter->ctxt.delta == NULL) {
+		iter->hunk_curr = NULL;
+		iter->line_curr = NULL;
+	}
+
+	if (delta_ptr != NULL)
+		*delta_ptr = !error ? iter->ctxt.delta : NULL;
+
+	return error;
+}
+
+int git_diff_iterator_next_hunk(
+	git_diff_range **range_ptr,
+	const char **header,
+	size_t *header_len,
+	git_diff_iterator *iter)
+{
+	int error = diffiter_do_diff_file(iter);
+	git_diff_range *range;
+
+	if (error)
+		return error;
+
+	if (iter->hunk_curr == NULL) {
+		if (range_ptr) *range_ptr = NULL;
+		if (header) *header = NULL;
+		if (header_len) *header_len = 0;
+		iter->line_curr = NULL;
+		return GIT_ITEROVER;
+	}
+
+	range = &iter->hunk_curr->range;
+
+	if (range_ptr)
+		*range_ptr = range;
+
+	if (header) {
+		int out = format_hunk_header(
+			iter->hunk_header, sizeof(iter->hunk_header), range);
+
+		/* TODO: append function name to header */
+
+		*(iter->hunk_header + out++) = '\n';
+
+		*header = iter->hunk_header;
+
+		if (header_len)
+			*header_len = (size_t)out;
+	}
+
+	iter->line_curr = iter->hunk_curr->line_head;
+	iter->hunk_curr = iter->hunk_curr->next;
+
+	return error;
+}
+
+int git_diff_iterator_next_line(
+	char *line_origin, /**< GIT_DIFF_LINE_... value from above */
+	const char **content_ptr,
+	size_t *content_len,
+	git_diff_iterator *iter)
+{
+	int error = diffiter_do_diff_file(iter);
+
+	if (error)
+		return error;
+
+	/* if the user has not called next_hunk yet, call it implicitly (OK?) */
+	if (iter->hunk_curr == iter->hunk_head) {
+		error = git_diff_iterator_next_hunk(NULL, NULL, NULL, iter);
+		if (error)
+			return error;
+	}
+
+	if (iter->line_curr == NULL) {
+		if (line_origin) *line_origin = GIT_DIFF_LINE_CONTEXT;
+		if (content_ptr) *content_ptr = NULL;
+		if (content_len) *content_len = 0;
+		return GIT_ITEROVER;
+	}
+
+	if (line_origin)
+		*line_origin = iter->line_curr->origin;
+	if (content_ptr)
+		*content_ptr = iter->line_curr->ptr;
+	if (content_len)
+		*content_len = iter->line_curr->len;
+
+	iter->line_curr = iter->line_curr->next;
+
+	return error;
 }
diff --git a/src/fetch.c b/src/fetch.c
index 278ba3c50..98e1f0b13 100644
--- a/src/fetch.c
+++ b/src/fetch.c
@@ -221,7 +221,7 @@ int git_fetch_negotiate(git_remote *remote)
 		}
 	}
 
-	if (error < 0 && error != GIT_REVWALKOVER)
+	if (error < 0 && error != GIT_ITEROVER)
 		goto on_error;
 
 	/* Tell the other end that we're done negotiating */
diff --git a/src/pool.h b/src/pool.h
index 05d339244..dee6ecdae 100644
--- a/src/pool.h
+++ b/src/pool.h
@@ -76,6 +76,17 @@ extern void git_pool_swap(git_pool *a, git_pool *b);
 extern void *git_pool_malloc(git_pool *pool, uint32_t items);
 
 /**
+ * Allocate space and zero it out.
+ */
+GIT_INLINE(void *) git_pool_mallocz(git_pool *pool, uint32_t items)
+{
+	void *ptr = git_pool_malloc(pool, items);
+	if (ptr)
+		memset(ptr, 0, (size_t)items * (size_t)pool->item_size);
+	return ptr;
+}
+
+/**
  * Allocate space and duplicate string data into it.
  *
  * This is allowed only for pools with item_size == sizeof(char)
diff --git a/src/refs.c b/src/refs.c
index 1589bc37d..211a5870c 100644
--- a/src/refs.c
+++ b/src/refs.c
@@ -1643,7 +1643,6 @@ int git_reference_normalize_name(
 			}
 		}
 
-
 		*buffer_out++ = *current++;
 		buffer_size--;
 	}
diff --git a/src/revparse.c b/src/revparse.c
index 3855c29f1..17266b944 100644
--- a/src/revparse.c
+++ b/src/revparse.c
@@ -493,7 +493,7 @@ static int walk_and_search(git_object **out, git_revwalk *walk, regex_t *regex)
 		git_object_free(obj);
 	}
 
-	if (error < 0 && error == GIT_REVWALKOVER)
+	if (error < 0 && error == GIT_ITEROVER)
 		error = GIT_ENOTFOUND;
 
 	return error;
diff --git a/src/revwalk.c b/src/revwalk.c
index 8b0e93baf..1a0927719 100644
--- a/src/revwalk.c
+++ b/src/revwalk.c
@@ -449,6 +449,7 @@ int git_merge_base(git_oid *out, git_repository *repo, git_oid *one, git_oid *tw
 
 	if (!result) {
 		git_revwalk_free(walk);
+		giterr_clear();
 		return GIT_ENOTFOUND;
 	}
 
@@ -682,7 +683,8 @@ static int revwalk_next_timesort(commit_object **object_out, git_revwalk *walk)
 		}
 	}
 
-	return GIT_REVWALKOVER;
+	giterr_clear();
+	return GIT_ITEROVER;
 }
 
 static int revwalk_next_unsorted(commit_object **object_out, git_revwalk *walk)
@@ -700,7 +702,8 @@ static int revwalk_next_unsorted(commit_object **object_out, git_revwalk *walk)
 		}
 	}
 
-	return GIT_REVWALKOVER;
+	giterr_clear();
+	return GIT_ITEROVER;
 }
 
 static int revwalk_next_toposort(commit_object **object_out, git_revwalk *walk)
@@ -710,8 +713,10 @@ static int revwalk_next_toposort(commit_object **object_out, git_revwalk *walk)
 
 	for (;;) {
 		next = commit_list_pop(&walk->iterator_topo);
-		if (next == NULL)
-			return GIT_REVWALKOVER;
+		if (next == NULL) {
+			giterr_clear();
+			return GIT_ITEROVER;
+		}
 
 		if (next->in_degree > 0) {
 			next->topo_delay = 1;
@@ -736,7 +741,7 @@ static int revwalk_next_toposort(commit_object **object_out, git_revwalk *walk)
 static int revwalk_next_reverse(commit_object **object_out, git_revwalk *walk)
 {
 	*object_out = commit_list_pop(&walk->iterator_reverse);
-	return *object_out ? 0 : GIT_REVWALKOVER;
+	return *object_out ? 0 : GIT_ITEROVER;
 }
 
 
@@ -751,8 +756,10 @@ static int prepare_walk(git_revwalk *walk)
 	 * If walk->one is NULL, there were no positive references,
 	 * so we know that the walk is already over.
 	 */
-	if (walk->one == NULL)
-		return GIT_REVWALKOVER;
+	if (walk->one == NULL) {
+		giterr_clear();
+		return GIT_ITEROVER;
+	}
 
 	/* first figure out what the merge bases are */
 	if (merge_bases_many(&bases, walk, walk->one, &walk->twos) < 0)
@@ -780,7 +787,7 @@ static int prepare_walk(git_revwalk *walk)
 				return -1;
 		}
 
-		if (error != GIT_REVWALKOVER)
+		if (error != GIT_ITEROVER)
 			return error;
 
 		walk->get_next = &revwalk_next_toposort;
@@ -792,7 +799,7 @@ static int prepare_walk(git_revwalk *walk)
 			if (commit_list_insert(next, &walk->iterator_reverse) == NULL)
 				return -1;
 
-		if (error != GIT_REVWALKOVER)
+		if (error != GIT_ITEROVER)
 			return error;
 
 		walk->get_next = &revwalk_next_reverse;
@@ -891,9 +898,10 @@ int git_revwalk_next(git_oid *oid, git_revwalk *walk)
 
 	error = walk->get_next(&next, walk);
 
-	if (error == GIT_REVWALKOVER) {
+	if (error == GIT_ITEROVER) {
 		git_revwalk_reset(walk);
-		return GIT_REVWALKOVER;
+		giterr_clear();
+		return GIT_ITEROVER;
 	}
 
 	if (!error)
diff --git a/src/status.c b/src/status.c
index 3d3d15d77..0a5fbdcbf 100644
--- a/src/status.c
+++ b/src/status.c
@@ -151,6 +151,9 @@ cleanup:
 	git_diff_list_free(idx2head);
 	git_diff_list_free(wd2idx);
 
+	if (err == GIT_EUSER)
+		giterr_clear();
+
 	return err;
 }
 
diff --git a/src/submodule.c b/src/submodule.c
index a9de9ee6e..66f1f84b4 100644
--- a/src/submodule.c
+++ b/src/submodule.c
@@ -163,6 +163,7 @@ int git_submodule_foreach(
 		}
 
 		if (callback(sm, sm->name, payload)) {
+			giterr_clear();
 			error = GIT_EUSER;
 			break;
 		}