Add git notes API

This commit adds basic git notes support to libgit2, namely:

* git_note_read
* git_note_message
* git_note_oid
* git_note_create
* git_note_remove

In the long run, we probably want to provide some convenience callback
mechanism for merging and moving (filter-branch) notes.

Signed-off-by: schu <schu-github@schulog.org>

2 files changed, 467 insertions, 0 deletions

diff --git a/src/notes.c b/src/notes.c
new file mode 100644
index 000000000..81fc00361
--- /dev/null
+++ b/src/notes.c
@@ -0,0 +1,439 @@
+/*
+ * Copyright (C) 2009-2012 the libgit2 contributors
+ *
+ * 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 "notes.h"
+
+#include "git2.h"
+#include "refs.h"
+
+static int find_subtree(git_tree **subtree, const git_oid *root,
+			git_repository *repo, const char *target, int *fanout)
+{
+	int error;
+	unsigned int i;
+	git_tree *tree;
+	const git_tree_entry *entry;
+
+	*subtree = NULL;
+
+	error = git_tree_lookup(&tree, repo, root);
+	if (error < GIT_SUCCESS) {
+		if (error == GIT_ENOTFOUND)
+			return error; /* notes tree doesn't exist yet */
+		return git__rethrow(error, "Failed to open notes tree");
+	}
+
+	for (i=0; i<git_tree_entrycount(tree); i++) {
+		entry = git_tree_entry_byindex(tree, i);
+
+		if (!git__ishex(git_tree_entry_name(entry)))
+			continue;
+
+		/*
+		 * A notes tree follows a strict byte-based progressive fanout
+		 * (i.e. using 2/38, 2/2/36, etc. fanouts, not e.g. 4/36 fanout)
+		 */
+
+		if (S_ISDIR(git_tree_entry_attributes(entry))
+			&& strlen(git_tree_entry_name(entry)) == 2
+			&& !strncmp(git_tree_entry_name(entry), target + *fanout, 2)) {
+
+			/* found matching subtree - unpack and resume lookup */
+
+			git_oid subtree_sha;
+			git_oid_cpy(&subtree_sha, git_tree_entry_id(entry));
+			git_tree_free(tree);
+
+			*fanout += 2;
+
+			return find_subtree(subtree, &subtree_sha, repo,
+					    target, fanout);
+		}
+	}
+
+	*subtree = tree;
+	return GIT_SUCCESS;
+}
+
+static int find_blob(git_oid *blob, git_tree *tree, const char *target)
+{
+	unsigned int i;
+	const git_tree_entry *entry;
+
+	for (i=0; i<git_tree_entrycount(tree); i++) {
+		entry = git_tree_entry_byindex(tree, i);
+
+		if (!strcmp(git_tree_entry_name(entry), target)) {
+			/* found matching note object - return */
+
+			git_oid_cpy(blob, git_tree_entry_id(entry));
+			return GIT_SUCCESS;
+		}
+	}
+	return GIT_ENOTFOUND;
+}
+
+static int note_write(git_oid *out, git_repository *repo,
+		      git_signature *author, git_signature *committer,
+		      const char *notes_ref, const char *note,
+		      const git_oid *tree_sha, const char *target,
+		      int nparents, git_commit **parents)
+{
+	int error, fanout = 0;
+	git_oid oid;
+	git_tree *tree = NULL;
+	git_tree_entry *entry;
+	git_treebuilder *tb;
+
+	/* check for existing notes tree */
+
+	if (tree_sha) {
+		error = find_subtree(&tree, tree_sha, repo, target, &fanout);
+		if (error < GIT_SUCCESS)
+			return git__rethrow(error, "Failed to lookup subtree");
+
+		error = find_blob(&oid, tree, target + fanout);
+		if (error < GIT_SUCCESS && error != GIT_ENOTFOUND) {
+			git_tree_free(tree);
+			return git__throw(GIT_ENOTFOUND, "Failed to read subtree %s", target);
+		}
+
+		if (error == GIT_SUCCESS) {
+			git_tree_free(tree);
+			return git__throw(GIT_EEXISTS, "Note for `%s` exists already", target);
+		}
+	}
+
+	/* no matching tree entry - add note object to target tree */
+
+	error = git_treebuilder_create(&tb, tree);
+	git_tree_free(tree);
+
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to create treebuilder");
+
+	if (!tree_sha)
+		/* no notes tree yet - create fanout */
+		fanout += 2;
+
+	/* create note object */
+	error = git_blob_create_frombuffer(&oid, repo, note, strlen(note));
+	if (error < GIT_SUCCESS) {
+		git_treebuilder_free(tb);
+		return git__rethrow(error, "Failed to create note object");
+	}
+
+	error = git_treebuilder_insert(&entry, tb, target + fanout, &oid, 0100644);
+	if (error < GIT_SUCCESS) {
+		/* libgit2 doesn't support object removal (gc) yet */
+		/* we leave an orphaned blob object behind - TODO */
+
+		git_treebuilder_free(tb);
+		return git__rethrow(error, "Failed to insert note object");
+	}
+
+	if (out)
+		git_oid_cpy(out, git_tree_entry_id(entry));
+
+	error = git_treebuilder_write(&oid, repo, tb);
+	git_treebuilder_free(tb);
+
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to write notes tree");
+
+	if (!tree_sha) {
+		/* create fanout subtree */
+
+		char subtree[3];
+		strncpy(subtree, target, 2);
+		subtree[2] = '\0';
+
+		error = git_treebuilder_create(&tb, NULL);
+		if (error < GIT_SUCCESS)
+			return git__rethrow(error, "Failed to create treebuilder");
+
+		error = git_treebuilder_insert(NULL, tb, subtree, &oid, 0040000);
+		if (error < GIT_SUCCESS) {
+			git_treebuilder_free(tb);
+			return git__rethrow(error, "Failed to insert note object");
+		}
+
+		error = git_treebuilder_write(&oid, repo, tb);
+		git_treebuilder_free(tb);
+
+		if (error < GIT_SUCCESS)
+			return git__rethrow(error, "Failed to write notes tree");
+	}
+
+	/* create new notes commit */
+
+	error = git_tree_lookup(&tree, repo, &oid);
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to open new notes tree");
+
+	error = git_commit_create(&oid, repo, notes_ref, author, committer,
+				  NULL, GIT_NOTES_DEFAULT_MSG_ADD,
+				  tree, nparents, (const git_commit **) parents);
+
+	git_tree_free(tree);
+
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to create new notes commit");
+
+	return GIT_SUCCESS;
+}
+
+static int note_lookup(git_note **out, git_repository *repo,
+		       const git_oid *tree_sha, const char *target)
+{
+	int error, fanout = 0;
+	git_oid oid;
+	git_blob *blob;
+	git_tree *tree;
+	git_note *note;
+
+	error = find_subtree(&tree, tree_sha, repo, target, &fanout);
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to lookup subtree");
+
+	error = find_blob(&oid, tree, target + fanout);
+	if (error < GIT_SUCCESS) {
+		git_tree_free(tree);
+		return git__throw(GIT_ENOTFOUND, "No note found for object %s",
+				  target);
+	}
+	git_tree_free(tree);
+
+	error = git_blob_lookup(&blob, repo, &oid);
+	if (error < GIT_SUCCESS)
+		return git__throw(GIT_ERROR, "Failed to lookup note object");
+
+	note = git__malloc(sizeof(git_note));
+	if (note == NULL) {
+		git_blob_free(blob);
+		return GIT_ENOMEM;
+	}
+
+	git_oid_cpy(&note->oid, &oid);
+	note->message = git__strdup(git_blob_rawcontent(blob));
+	if (note->message == NULL)
+		error = GIT_ENOMEM;
+
+	*out = note;
+
+	git_blob_free(blob);
+	return error;
+}
+
+static int note_remove(git_repository *repo,
+		       git_signature *author, git_signature *committer,
+		       const char *notes_ref, const git_oid *tree_sha,
+		       const char *target, int nparents, git_commit **parents)
+{
+	int error, fanout = 0;
+	git_oid oid;
+	git_tree *tree;
+	git_treebuilder *tb;
+
+	error = find_subtree(&tree, tree_sha, repo, target, &fanout);
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to lookup subtree");
+
+	error = find_blob(&oid, tree, target + fanout);
+	if (error < GIT_SUCCESS) {
+		git_tree_free(tree);
+		return git__throw(GIT_ENOTFOUND, "No note found for object %s",
+				  target);
+	}
+
+	error = git_treebuilder_create(&tb, tree);
+	git_tree_free(tree);
+
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to create treebuilder");
+
+	error = git_treebuilder_remove(tb, target + fanout);
+	if (error < GIT_SUCCESS) {
+		git_treebuilder_free(tb);
+		return git__rethrow(error, "Failed to remove entry from notes tree");
+	}
+
+	error = git_treebuilder_write(&oid, repo, tb);
+	git_treebuilder_free(tb);
+
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to write notes tree");
+
+	/* create new notes commit */
+
+	error = git_tree_lookup(&tree, repo, &oid);
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to open new notes tree");
+
+	error = git_commit_create(&oid, repo, notes_ref, author, committer,
+				  NULL, GIT_NOTES_DEFAULT_MSG_RM,
+				  tree, nparents, (const git_commit **) parents);
+
+	git_tree_free(tree);
+
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to create new notes commit");
+
+	return error;
+}
+
+int git_note_read(git_note **out, git_repository *repo,
+		  const char *notes_ref, const git_oid *oid)
+{
+	int error;
+	char *target;
+	git_reference *ref;
+	git_commit *commit;
+	const git_oid *sha;
+
+	*out = NULL;
+
+	if (!notes_ref)
+		notes_ref = GIT_NOTES_DEFAULT_REF;
+
+	error = git_reference_lookup(&ref, repo, notes_ref);
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to lookup reference `%s`", notes_ref);
+
+	assert(git_ref_type(ref) == GIT_REF_OID);
+
+	sha = git_reference_oid(ref);
+	error = git_commit_lookup(&commit, repo, sha);
+
+	git_reference_free(ref);
+
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to find notes commit object");
+
+	sha = git_commit_tree_oid(commit);
+	git_commit_free(commit);
+
+	target = git_oid_allocfmt(oid);
+	if (target == NULL)
+		return GIT_ENOMEM;
+
+	error = note_lookup(out, repo, sha, target);
+
+	git__free(target);
+	return error == GIT_SUCCESS ? GIT_SUCCESS :
+		git__rethrow(error, "Failed to read note");
+}
+
+int git_note_create(git_oid *out, git_repository *repo,
+		    git_signature *author, git_signature *committer,
+		    const char *notes_ref, const git_oid *oid,
+		     const char *note)
+{
+	int error, nparents = 0;
+	char *target;
+	git_oid sha;
+	git_commit *commit = NULL;
+	git_reference *ref;
+
+	if (!notes_ref)
+		notes_ref = GIT_NOTES_DEFAULT_REF;
+
+	error = git_reference_lookup(&ref, repo, notes_ref);
+	if (error < GIT_SUCCESS && error != GIT_ENOTFOUND)
+		return git__rethrow(error, "Failed to lookup reference `%s`", notes_ref);
+
+	if (error == GIT_SUCCESS) {
+		assert(git_ref_type(ref) == GIT_REF_OID);
+
+		/* lookup existing notes tree oid */
+
+		git_oid_cpy(&sha, git_reference_oid(ref));
+		git_reference_free(ref);
+
+		error = git_commit_lookup(&commit, repo, &sha);
+		if (error < GIT_SUCCESS)
+			return git__rethrow(error, "Failed to find notes commit object");
+
+		git_oid_cpy(&sha, git_commit_tree_oid(commit));
+		nparents++;
+	}
+
+	target = git_oid_allocfmt(oid);
+	if (target == NULL)
+		return GIT_ENOMEM;
+
+	error = note_write(out, repo, author, committer, notes_ref,
+			   note, nparents ? &sha : NULL, target,
+			   nparents, &commit);
+
+	git__free(target);
+	git_commit_free(commit);
+	return error == GIT_SUCCESS ? GIT_SUCCESS :
+		git__rethrow(error, "Failed to write note");
+}
+
+int git_note_remove(git_repository *repo, const char *notes_ref,
+		    git_signature *author, git_signature *committer,
+		    const git_oid *oid)
+{
+	int error;
+	char *target;
+	git_oid sha;
+	git_commit *commit;
+	git_reference *ref;
+
+	if (!notes_ref)
+		notes_ref = GIT_NOTES_DEFAULT_REF;
+
+	error = git_reference_lookup(&ref, repo, notes_ref);
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to lookup reference `%s`", notes_ref);
+
+	assert(git_ref_type(ref) == GIT_REF_OID);
+
+	git_oid_cpy(&sha, git_reference_oid(ref));
+	git_reference_free(ref);
+
+	error = git_commit_lookup(&commit, repo, &sha);
+	if (error < GIT_SUCCESS)
+		return git__rethrow(error, "Failed to find notes commit object");
+
+	git_oid_cpy(&sha, git_commit_tree_oid(commit));
+
+	target = git_oid_allocfmt(oid);
+	if (target == NULL)
+		return GIT_ENOMEM;
+
+	error = note_remove(repo, author, committer, notes_ref,
+			    &sha, target, 1, &commit);
+
+	git__free(target);
+	git_commit_free(commit);
+	return error == GIT_SUCCESS ? GIT_SUCCESS :
+		git__rethrow(error, "Failed to read note");
+}
+
+const char * git_note_message(git_note *note)
+{
+	assert(note);
+	return note->message;
+}
+
+const git_oid * git_note_oid(git_note *note)
+{
+	assert(note);
+	return &note->oid;
+}
+
+void git_note_free(git_note *note)
+{
+	if (note == NULL)
+		return;
+
+	git__free(note->message);
+	git__free(note);
+}
diff --git a/src/notes.h b/src/notes.h
new file mode 100644
index 000000000..219db1ab0
--- /dev/null
+++ b/src/notes.h
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2009-2012 the libgit2 contributors
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_note_h__
+#define INCLUDE_note_h__
+
+#include "common.h"
+
+#include "git2/oid.h"
+
+#define GIT_NOTES_DEFAULT_REF "refs/notes/commits"
+
+#define GIT_NOTES_DEFAULT_MSG_ADD \
+	"Notes added by 'git_note_create' from libgit2"
+
+#define GIT_NOTES_DEFAULT_MSG_RM \
+	"Notes removed by 'git_note_remove' from libgit2"
+
+struct git_note {
+	git_oid oid;
+
+	char *message;
+};
+
+#endif /* INCLUDE_notes_h__ */