git notes merge: Manual conflict resolution, part 2/2

When the notes merge conflicts in .git/NOTES_MERGE_WORKTREE have been
resolved, we need to record a new notes commit on the appropriate notes
ref with the resolved notes.

This patch implements 'git notes merge --commit' which the user should
run after resolving conflicts in the notes merge worktree. This command
finalizes the notes merge by recombining the partial notes tree from
part 1 with the now-resolved conflicts in the notes merge worktree in a
merge commit, and updating the appropriate ref to this merge commit.

In order to correctly finalize the merge, we need to keep track of three
things:

- The partial merge result from part 1, containing the auto-merged notes.
  This is now stored into a ref called .git/NOTES_MERGE_PARTIAL.
- The unmerged notes. These are already stored in
  .git/NOTES_MERGE_WORKTREE, thanks to part 1.
- The notes ref to be updated by the finalized merge result. This is now
  stored in a symref called .git/NOTES_MERGE_REF.

In addition to "git notes merge --commit", which uses the above details
to create the finalized notes merge commit, this patch also implements
"git notes merge --reset", which aborts the ongoing notes merge by simply
removing the files/directory described above.

FTR, "git notes merge --commit" reuses "git notes merge --reset" to remove
the information described above (.git/NOTES_MERGE_*) after the notes merge
have been successfully finalized.

The patch also contains documentation and testcases for the two new options.

This patch has been improved by the following contributions:
- Ævar Arnfjörð Bjarmason: Fix nonsense sentence in --commit description
- Sverre Rabbelier: Rename --reset to --abort

Thanks-to: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Thanks-to: Sverre Rabbelier <srabbelier@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

notes-merge.c

@@ -278,7 +278,7 @@ static void check_notes_merge_worktree(struct notes_merge_options *o)
 				die("You have not concluded your previous "
 				    "notes merge (%s exists).\nPlease, use "
 				    "'git notes merge --commit' or 'git notes "
-				    "merge --reset' to commit/abort the "
+				    "merge --abort' to commit/abort the "
 				    "previous merge before you start a new "
 				    "notes merge.", git_path("NOTES_MERGE_*"));
 			else
@@ -650,3 +650,72 @@ found_result:
 	       result, sha1_to_hex(result_sha1));
 	return result;
 }
+
+int notes_merge_commit(struct notes_merge_options *o,
+		       struct notes_tree *partial_tree,
+		       struct commit *partial_commit,
+		       unsigned char *result_sha1)
+{
+	/*
+	 * Iterate through files in .git/NOTES_MERGE_WORKTREE and add all
+	 * found notes to 'partial_tree'. Write the updates notes tree to
+	 * the DB, and commit the resulting tree object while reusing the
+	 * commit message and parents from 'partial_commit'.
+	 * Finally store the new commit object SHA1 into 'result_sha1'.
+	 */
+	struct dir_struct dir;
+	const char *path = git_path(NOTES_MERGE_WORKTREE "/");
+	int path_len = strlen(path), i;
+	const char *msg = strstr(partial_commit->buffer, "\n\n");
+
+	OUTPUT(o, 3, "Committing notes in notes merge worktree at %.*s",
+	       path_len - 1, path);
+
+	if (!msg || msg[2] == '\0')
+		die("partial notes commit has empty message");
+	msg += 2;
+
+	memset(&dir, 0, sizeof(dir));
+	read_directory(&dir, path, path_len, NULL);
+	for (i = 0; i < dir.nr; i++) {
+		struct dir_entry *ent = dir.entries[i];
+		struct stat st;
+		const char *relpath = ent->name + path_len;
+		unsigned char obj_sha1[20], blob_sha1[20];
+
+		if (ent->len - path_len != 40 || get_sha1_hex(relpath, obj_sha1)) {
+			OUTPUT(o, 3, "Skipping non-SHA1 entry '%s'", ent->name);
+			continue;
+		}
+
+		/* write file as blob, and add to partial_tree */
+		if (stat(ent->name, &st))
+			die_errno("Failed to stat '%s'", ent->name);
+		if (index_path(blob_sha1, ent->name, &st, 1))
+			die("Failed to write blob object from '%s'", ent->name);
+		if (add_note(partial_tree, obj_sha1, blob_sha1, NULL))
+			die("Failed to add resolved note '%s' to notes tree",
+			    ent->name);
+		OUTPUT(o, 4, "Added resolved note for object %s: %s",
+		       sha1_to_hex(obj_sha1), sha1_to_hex(blob_sha1));
+	}
+
+	create_notes_commit(partial_tree, partial_commit->parents, msg,
+			    result_sha1);
+	OUTPUT(o, 4, "Finalized notes merge commit: %s",
+	       sha1_to_hex(result_sha1));
+	return 0;
+}
+
+int notes_merge_abort(struct notes_merge_options *o)
+{
+	/* Remove .git/NOTES_MERGE_WORKTREE directory and all files within */
+	struct strbuf buf = STRBUF_INIT;
+	int ret;
+
+	strbuf_addstr(&buf, git_path(NOTES_MERGE_WORKTREE));
+	OUTPUT(o, 3, "Removing notes merge worktree at %s", buf.buf);
+	ret = remove_dir_recursively(&buf, 0);
+	strbuf_release(&buf);
+	return ret;
+}