Squashed 'third_party/git/' content from commit cb71568594

git-subtree-dir: third_party/git
git-subtree-split: cb715685942260375e1eb8153b0768a376e4ece7

1 files changed, 754 insertions, 0 deletions

diff --git a/notes-merge.c b/notes-merge.c
new file mode 100644
index 0000000000..2fe724f1cf
--- /dev/null
+++ b/notes-merge.c
@@ -0,0 +1,754 @@
+#include "cache.h"
+#include "commit.h"
+#include "refs.h"
+#include "object-store.h"
+#include "repository.h"
+#include "diff.h"
+#include "diffcore.h"
+#include "xdiff-interface.h"
+#include "ll-merge.h"
+#include "dir.h"
+#include "notes.h"
+#include "notes-merge.h"
+#include "strbuf.h"
+#include "notes-utils.h"
+#include "commit-reach.h"
+
+struct notes_merge_pair {
+	struct object_id obj, base, local, remote;
+};
+
+void init_notes_merge_options(struct repository *r,
+			      struct notes_merge_options *o)
+{
+	memset(o, 0, sizeof(struct notes_merge_options));
+	strbuf_init(&(o->commit_msg), 0);
+	o->verbosity = NOTES_MERGE_VERBOSITY_DEFAULT;
+	o->repo = r;
+}
+
+static int path_to_oid(const char *path, struct object_id *oid)
+{
+	char hex_oid[GIT_MAX_HEXSZ];
+	int i = 0;
+	while (*path && i < the_hash_algo->hexsz) {
+		if (*path != '/')
+			hex_oid[i++] = *path;
+		path++;
+	}
+	if (*path || i != the_hash_algo->hexsz)
+		return -1;
+	return get_oid_hex(hex_oid, oid);
+}
+
+static int verify_notes_filepair(struct diff_filepair *p, struct object_id *oid)
+{
+	switch (p->status) {
+	case DIFF_STATUS_MODIFIED:
+		assert(p->one->mode == p->two->mode);
+		assert(!is_null_oid(&p->one->oid));
+		assert(!is_null_oid(&p->two->oid));
+		break;
+	case DIFF_STATUS_ADDED:
+		assert(is_null_oid(&p->one->oid));
+		break;
+	case DIFF_STATUS_DELETED:
+		assert(is_null_oid(&p->two->oid));
+		break;
+	default:
+		return -1;
+	}
+	assert(!strcmp(p->one->path, p->two->path));
+	return path_to_oid(p->one->path, oid);
+}
+
+static struct notes_merge_pair *find_notes_merge_pair_pos(
+		struct notes_merge_pair *list, int len, struct object_id *obj,
+		int insert_new, int *occupied)
+{
+	/*
+	 * Both diff_tree_remote() and diff_tree_local() tend to process
+	 * merge_pairs in ascending order. Therefore, cache last returned
+	 * index, and search sequentially from there until the appropriate
+	 * position is found.
+	 *
+	 * Since inserts only happen from diff_tree_remote() (which mainly
+	 * _appends_), we don't care that inserting into the middle of the
+	 * list is expensive (using memmove()).
+	 */
+	static int last_index;
+	int i = last_index < len ? last_index : len - 1;
+	int prev_cmp = 0, cmp = -1;
+	while (i >= 0 && i < len) {
+		cmp = oidcmp(obj, &list[i].obj);
+		if (!cmp) /* obj belongs @ i */
+			break;
+		else if (cmp < 0 && prev_cmp <= 0) /* obj belongs < i */
+			i--;
+		else if (cmp < 0) /* obj belongs between i-1 and i */
+			break;
+		else if (cmp > 0 && prev_cmp >= 0) /* obj belongs > i */
+			i++;
+		else /* if (cmp > 0) */ { /* obj belongs between i and i+1 */
+			i++;
+			break;
+		}
+		prev_cmp = cmp;
+	}
+	if (i < 0)
+		i = 0;
+	/* obj belongs at, or immediately preceding, index i (0 <= i <= len) */
+
+	if (!cmp)
+		*occupied = 1;
+	else {
+		*occupied = 0;
+		if (insert_new && i < len) {
+			MOVE_ARRAY(list + i + 1, list + i, len - i);
+			memset(list + i, 0, sizeof(struct notes_merge_pair));
+		}
+	}
+	last_index = i;
+	return list + i;
+}
+
+static struct object_id uninitialized = {
+	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
+	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
+};
+
+static struct notes_merge_pair *diff_tree_remote(struct notes_merge_options *o,
+						 const struct object_id *base,
+						 const struct object_id *remote,
+						 int *num_changes)
+{
+	struct diff_options opt;
+	struct notes_merge_pair *changes;
+	int i, len = 0;
+
+	trace_printf("\tdiff_tree_remote(base = %.7s, remote = %.7s)\n",
+	       oid_to_hex(base), oid_to_hex(remote));
+
+	repo_diff_setup(o->repo, &opt);
+	opt.flags.recursive = 1;
+	opt.output_format = DIFF_FORMAT_NO_OUTPUT;
+	diff_setup_done(&opt);
+	diff_tree_oid(base, remote, "", &opt);
+	diffcore_std(&opt);
+
+	changes = xcalloc(diff_queued_diff.nr, sizeof(struct notes_merge_pair));
+
+	for (i = 0; i < diff_queued_diff.nr; i++) {
+		struct diff_filepair *p = diff_queued_diff.queue[i];
+		struct notes_merge_pair *mp;
+		int occupied;
+		struct object_id obj;
+
+		if (verify_notes_filepair(p, &obj)) {
+			trace_printf("\t\tCannot merge entry '%s' (%c): "
+			       "%.7s -> %.7s. Skipping!\n", p->one->path,
+			       p->status, oid_to_hex(&p->one->oid),
+			       oid_to_hex(&p->two->oid));
+			continue;
+		}
+		mp = find_notes_merge_pair_pos(changes, len, &obj, 1, &occupied);
+		if (occupied) {
+			/* We've found an addition/deletion pair */
+			assert(oideq(&mp->obj, &obj));
+			if (is_null_oid(&p->one->oid)) { /* addition */
+				assert(is_null_oid(&mp->remote));
+				oidcpy(&mp->remote, &p->two->oid);
+			} else if (is_null_oid(&p->two->oid)) { /* deletion */
+				assert(is_null_oid(&mp->base));
+				oidcpy(&mp->base, &p->one->oid);
+			} else
+				assert(!"Invalid existing change recorded");
+		} else {
+			oidcpy(&mp->obj, &obj);
+			oidcpy(&mp->base, &p->one->oid);
+			oidcpy(&mp->local, &uninitialized);
+			oidcpy(&mp->remote, &p->two->oid);
+			len++;
+		}
+		trace_printf("\t\tStored remote change for %s: %.7s -> %.7s\n",
+		       oid_to_hex(&mp->obj), oid_to_hex(&mp->base),
+		       oid_to_hex(&mp->remote));
+	}
+	diff_flush(&opt);
+	clear_pathspec(&opt.pathspec);
+
+	*num_changes = len;
+	return changes;
+}
+
+static void diff_tree_local(struct notes_merge_options *o,
+			    struct notes_merge_pair *changes, int len,
+			    const struct object_id *base,
+			    const struct object_id *local)
+{
+	struct diff_options opt;
+	int i;
+
+	trace_printf("\tdiff_tree_local(len = %i, base = %.7s, local = %.7s)\n",
+	       len, oid_to_hex(base), oid_to_hex(local));
+
+	repo_diff_setup(o->repo, &opt);
+	opt.flags.recursive = 1;
+	opt.output_format = DIFF_FORMAT_NO_OUTPUT;
+	diff_setup_done(&opt);
+	diff_tree_oid(base, local, "", &opt);
+	diffcore_std(&opt);
+
+	for (i = 0; i < diff_queued_diff.nr; i++) {
+		struct diff_filepair *p = diff_queued_diff.queue[i];
+		struct notes_merge_pair *mp;
+		int match;
+		struct object_id obj;
+
+		if (verify_notes_filepair(p, &obj)) {
+			trace_printf("\t\tCannot merge entry '%s' (%c): "
+			       "%.7s -> %.7s. Skipping!\n", p->one->path,
+			       p->status, oid_to_hex(&p->one->oid),
+			       oid_to_hex(&p->two->oid));
+			continue;
+		}
+		mp = find_notes_merge_pair_pos(changes, len, &obj, 0, &match);
+		if (!match) {
+			trace_printf("\t\tIgnoring local-only change for %s: "
+			       "%.7s -> %.7s\n", oid_to_hex(&obj),
+			       oid_to_hex(&p->one->oid),
+			       oid_to_hex(&p->two->oid));
+			continue;
+		}
+
+		assert(oideq(&mp->obj, &obj));
+		if (is_null_oid(&p->two->oid)) { /* deletion */
+			/*
+			 * Either this is a true deletion (1), or it is part
+			 * of an A/D pair (2), or D/A pair (3):
+			 *
+			 * (1) mp->local is uninitialized; set it to null_sha1
+			 * (2) mp->local is not uninitialized; don't touch it
+			 * (3) mp->local is uninitialized; set it to null_sha1
+			 *     (will be overwritten by following addition)
+			 */
+			if (oideq(&mp->local, &uninitialized))
+				oidclr(&mp->local);
+		} else if (is_null_oid(&p->one->oid)) { /* addition */
+			/*
+			 * Either this is a true addition (1), or it is part
+			 * of an A/D pair (2), or D/A pair (3):
+			 *
+			 * (1) mp->local is uninitialized; set to p->two->sha1
+			 * (2) mp->local is uninitialized; set to p->two->sha1
+			 * (3) mp->local is null_sha1;     set to p->two->sha1
+			 */
+			assert(is_null_oid(&mp->local) ||
+			       oideq(&mp->local, &uninitialized));
+			oidcpy(&mp->local, &p->two->oid);
+		} else { /* modification */
+			/*
+			 * This is a true modification. p->one->sha1 shall
+			 * match mp->base, and mp->local shall be uninitialized.
+			 * Set mp->local to p->two->sha1.
+			 */
+			assert(oideq(&p->one->oid, &mp->base));
+			assert(oideq(&mp->local, &uninitialized));
+			oidcpy(&mp->local, &p->two->oid);
+		}
+		trace_printf("\t\tStored local change for %s: %.7s -> %.7s\n",
+		       oid_to_hex(&mp->obj), oid_to_hex(&mp->base),
+		       oid_to_hex(&mp->local));
+	}
+	diff_flush(&opt);
+	clear_pathspec(&opt.pathspec);
+}
+
+static void check_notes_merge_worktree(struct notes_merge_options *o)
+{
+	if (!o->has_worktree) {
+		/*
+		 * Must establish NOTES_MERGE_WORKTREE.
+		 * Abort if NOTES_MERGE_WORKTREE already exists
+		 */
+		if (file_exists(git_path(NOTES_MERGE_WORKTREE)) &&
+		    !is_empty_dir(git_path(NOTES_MERGE_WORKTREE))) {
+			if (advice_resolve_conflict)
+				die(_("You have not concluded your previous "
+				    "notes merge (%s exists).\nPlease, use "
+				    "'git notes merge --commit' or 'git notes "
+				    "merge --abort' to commit/abort the "
+				    "previous merge before you start a new "
+				    "notes merge."), git_path("NOTES_MERGE_*"));
+			else
+				die(_("You have not concluded your notes merge "
+				    "(%s exists)."), git_path("NOTES_MERGE_*"));
+		}
+
+		if (safe_create_leading_directories_const(git_path(
+				NOTES_MERGE_WORKTREE "/.test")))
+			die_errno("unable to create directory %s",
+				  git_path(NOTES_MERGE_WORKTREE));
+		o->has_worktree = 1;
+	} else if (!file_exists(git_path(NOTES_MERGE_WORKTREE)))
+		/* NOTES_MERGE_WORKTREE should already be established */
+		die("missing '%s'. This should not happen",
+		    git_path(NOTES_MERGE_WORKTREE));
+}
+
+static void write_buf_to_worktree(const struct object_id *obj,
+				  const char *buf, unsigned long size)
+{
+	int fd;
+	char *path = git_pathdup(NOTES_MERGE_WORKTREE "/%s", oid_to_hex(obj));
+	if (safe_create_leading_directories_const(path))
+		die_errno("unable to create directory for '%s'", path);
+
+	fd = xopen(path, O_WRONLY | O_EXCL | O_CREAT, 0666);
+
+	while (size > 0) {
+		ssize_t ret = write_in_full(fd, buf, size);
+		if (ret < 0) {
+			/* Ignore epipe */
+			if (errno == EPIPE)
+				break;
+			die_errno("notes-merge");
+		}
+		size -= ret;
+		buf += ret;
+	}
+
+	close(fd);
+	free(path);
+}
+
+static void write_note_to_worktree(const struct object_id *obj,
+				   const struct object_id *note)
+{
+	enum object_type type;
+	unsigned long size;
+	void *buf = read_object_file(note, &type, &size);
+
+	if (!buf)
+		die("cannot read note %s for object %s",
+		    oid_to_hex(note), oid_to_hex(obj));
+	if (type != OBJ_BLOB)
+		die("blob expected in note %s for object %s",
+		    oid_to_hex(note), oid_to_hex(obj));
+	write_buf_to_worktree(obj, buf, size);
+	free(buf);
+}
+
+static int ll_merge_in_worktree(struct notes_merge_options *o,
+				struct notes_merge_pair *p)
+{
+	mmbuffer_t result_buf;
+	mmfile_t base, local, remote;
+	int status;
+
+	read_mmblob(&base, &p->base);
+	read_mmblob(&local, &p->local);
+	read_mmblob(&remote, &p->remote);
+
+	status = ll_merge(&result_buf, oid_to_hex(&p->obj), &base, NULL,
+			  &local, o->local_ref, &remote, o->remote_ref,
+			  o->repo->index, NULL);
+
+	free(base.ptr);
+	free(local.ptr);
+	free(remote.ptr);
+
+	if ((status < 0) || !result_buf.ptr)
+		die("Failed to execute internal merge");
+
+	write_buf_to_worktree(&p->obj, result_buf.ptr, result_buf.size);
+	free(result_buf.ptr);
+
+	return status;
+}
+
+static int merge_one_change_manual(struct notes_merge_options *o,
+				   struct notes_merge_pair *p,
+				   struct notes_tree *t)
+{
+	const char *lref = o->local_ref ? o->local_ref : "local version";
+	const char *rref = o->remote_ref ? o->remote_ref : "remote version";
+
+	trace_printf("\t\t\tmerge_one_change_manual(obj = %.7s, base = %.7s, "
+	       "local = %.7s, remote = %.7s)\n",
+	       oid_to_hex(&p->obj), oid_to_hex(&p->base),
+	       oid_to_hex(&p->local), oid_to_hex(&p->remote));
+
+	/* add "Conflicts:" section to commit message first time through */
+	if (!o->has_worktree)
+		strbuf_addstr(&(o->commit_msg), "\n\nConflicts:\n");
+
+	strbuf_addf(&(o->commit_msg), "\t%s\n", oid_to_hex(&p->obj));
+
+	if (o->verbosity >= 2)
+		printf("Auto-merging notes for %s\n", oid_to_hex(&p->obj));
+	check_notes_merge_worktree(o);
+	if (is_null_oid(&p->local)) {
+		/* D/F conflict, checkout p->remote */
+		assert(!is_null_oid(&p->remote));
+		if (o->verbosity >= 1)
+			printf("CONFLICT (delete/modify): Notes for object %s "
+				"deleted in %s and modified in %s. Version from %s "
+				"left in tree.\n",
+				oid_to_hex(&p->obj), lref, rref, rref);
+		write_note_to_worktree(&p->obj, &p->remote);
+	} else if (is_null_oid(&p->remote)) {
+		/* D/F conflict, checkout p->local */
+		assert(!is_null_oid(&p->local));
+		if (o->verbosity >= 1)
+			printf("CONFLICT (delete/modify): Notes for object %s "
+				"deleted in %s and modified in %s. Version from %s "
+				"left in tree.\n",
+				oid_to_hex(&p->obj), rref, lref, lref);
+		write_note_to_worktree(&p->obj, &p->local);
+	} else {
+		/* "regular" conflict, checkout result of ll_merge() */
+		const char *reason = "content";
+		if (is_null_oid(&p->base))
+			reason = "add/add";
+		assert(!is_null_oid(&p->local));
+		assert(!is_null_oid(&p->remote));
+		if (o->verbosity >= 1)
+			printf("CONFLICT (%s): Merge conflict in notes for "
+				"object %s\n", reason,
+				oid_to_hex(&p->obj));
+		ll_merge_in_worktree(o, p);
+	}
+
+	trace_printf("\t\t\tremoving from partial merge result\n");
+	remove_note(t, p->obj.hash);
+
+	return 1;
+}
+
+static int merge_one_change(struct notes_merge_options *o,
+			    struct notes_merge_pair *p, struct notes_tree *t)
+{
+	/*
+	 * Return 0 if change is successfully resolved (stored in notes_tree).
+	 * Return 1 is change results in a conflict (NOT stored in notes_tree,
+	 * but instead written to NOTES_MERGE_WORKTREE with conflict markers).
+	 */
+	switch (o->strategy) {
+	case NOTES_MERGE_RESOLVE_MANUAL:
+		return merge_one_change_manual(o, p, t);
+	case NOTES_MERGE_RESOLVE_OURS:
+		if (o->verbosity >= 2)
+			printf("Using local notes for %s\n",
+						oid_to_hex(&p->obj));
+		/* nothing to do */
+		return 0;
+	case NOTES_MERGE_RESOLVE_THEIRS:
+		if (o->verbosity >= 2)
+			printf("Using remote notes for %s\n",
+						oid_to_hex(&p->obj));
+		if (add_note(t, &p->obj, &p->remote, combine_notes_overwrite))
+			BUG("combine_notes_overwrite failed");
+		return 0;
+	case NOTES_MERGE_RESOLVE_UNION:
+		if (o->verbosity >= 2)
+			printf("Concatenating local and remote notes for %s\n",
+							oid_to_hex(&p->obj));
+		if (add_note(t, &p->obj, &p->remote, combine_notes_concatenate))
+			die("failed to concatenate notes "
+			    "(combine_notes_concatenate)");
+		return 0;
+	case NOTES_MERGE_RESOLVE_CAT_SORT_UNIQ:
+		if (o->verbosity >= 2)
+			printf("Concatenating unique lines in local and remote "
+				"notes for %s\n", oid_to_hex(&p->obj));
+		if (add_note(t, &p->obj, &p->remote, combine_notes_cat_sort_uniq))
+			die("failed to concatenate notes "
+			    "(combine_notes_cat_sort_uniq)");
+		return 0;
+	}
+	die("Unknown strategy (%i).", o->strategy);
+}
+
+static int merge_changes(struct notes_merge_options *o,
+			 struct notes_merge_pair *changes, int *num_changes,
+			 struct notes_tree *t)
+{
+	int i, conflicts = 0;
+
+	trace_printf("\tmerge_changes(num_changes = %i)\n", *num_changes);
+	for (i = 0; i < *num_changes; i++) {
+		struct notes_merge_pair *p = changes + i;
+		trace_printf("\t\t%.7s: %.7s -> %.7s/%.7s\n",
+		       oid_to_hex(&p->obj), oid_to_hex(&p->base),
+		       oid_to_hex(&p->local),
+		       oid_to_hex(&p->remote));
+
+		if (oideq(&p->base, &p->remote)) {
+			/* no remote change; nothing to do */
+			trace_printf("\t\t\tskipping (no remote change)\n");
+		} else if (oideq(&p->local, &p->remote)) {
+			/* same change in local and remote; nothing to do */
+			trace_printf("\t\t\tskipping (local == remote)\n");
+		} else if (oideq(&p->local, &uninitialized) ||
+			   oideq(&p->local, &p->base)) {
+			/* no local change; adopt remote change */
+			trace_printf("\t\t\tno local change, adopted remote\n");
+			if (add_note(t, &p->obj, &p->remote,
+				     combine_notes_overwrite))
+				BUG("combine_notes_overwrite failed");
+		} else {
+			/* need file-level merge between local and remote */
+			trace_printf("\t\t\tneed content-level merge\n");
+			conflicts += merge_one_change(o, p, t);
+		}
+	}
+
+	return conflicts;
+}
+
+static int merge_from_diffs(struct notes_merge_options *o,
+			    const struct object_id *base,
+			    const struct object_id *local,
+			    const struct object_id *remote,
+			    struct notes_tree *t)
+{
+	struct notes_merge_pair *changes;
+	int num_changes, conflicts;
+
+	trace_printf("\tmerge_from_diffs(base = %.7s, local = %.7s, "
+	       "remote = %.7s)\n", oid_to_hex(base), oid_to_hex(local),
+	       oid_to_hex(remote));
+
+	changes = diff_tree_remote(o, base, remote, &num_changes);
+	diff_tree_local(o, changes, num_changes, base, local);
+
+	conflicts = merge_changes(o, changes, &num_changes, t);
+	free(changes);
+
+	if (o->verbosity >= 4)
+		printf(t->dirty ?
+		       "Merge result: %i unmerged notes and a dirty notes tree\n" :
+		       "Merge result: %i unmerged notes and a clean notes tree\n",
+		       conflicts);
+
+	return conflicts ? -1 : 1;
+}
+
+int notes_merge(struct notes_merge_options *o,
+		struct notes_tree *local_tree,
+		struct object_id *result_oid)
+{
+	struct object_id local_oid, remote_oid;
+	struct commit *local, *remote;
+	struct commit_list *bases = NULL;
+	const struct object_id *base_oid, *base_tree_oid;
+	int result = 0;
+
+	assert(o->local_ref && o->remote_ref);
+	assert(!strcmp(o->local_ref, local_tree->ref));
+	oidclr(result_oid);
+
+	trace_printf("notes_merge(o->local_ref = %s, o->remote_ref = %s)\n",
+	       o->local_ref, o->remote_ref);
+
+	/* Dereference o->local_ref into local_sha1 */
+	if (read_ref_full(o->local_ref, 0, &local_oid, NULL))
+		die("Failed to resolve local notes ref '%s'", o->local_ref);
+	else if (!check_refname_format(o->local_ref, 0) &&
+		is_null_oid(&local_oid))
+		local = NULL; /* local_oid == null_oid indicates unborn ref */
+	else if (!(local = lookup_commit_reference(o->repo, &local_oid)))
+		die("Could not parse local commit %s (%s)",
+		    oid_to_hex(&local_oid), o->local_ref);
+	trace_printf("\tlocal commit: %.7s\n", oid_to_hex(&local_oid));
+
+	/* Dereference o->remote_ref into remote_oid */
+	if (get_oid(o->remote_ref, &remote_oid)) {
+		/*
+		 * Failed to get remote_oid. If o->remote_ref looks like an
+		 * unborn ref, perform the merge using an empty notes tree.
+		 */
+		if (!check_refname_format(o->remote_ref, 0)) {
+			oidclr(&remote_oid);
+			remote = NULL;
+		} else {
+			die("Failed to resolve remote notes ref '%s'",
+			    o->remote_ref);
+		}
+	} else if (!(remote = lookup_commit_reference(o->repo, &remote_oid))) {
+		die("Could not parse remote commit %s (%s)",
+		    oid_to_hex(&remote_oid), o->remote_ref);
+	}
+	trace_printf("\tremote commit: %.7s\n", oid_to_hex(&remote_oid));
+
+	if (!local && !remote)
+		die("Cannot merge empty notes ref (%s) into empty notes ref "
+		    "(%s)", o->remote_ref, o->local_ref);
+	if (!local) {
+		/* result == remote commit */
+		oidcpy(result_oid, &remote_oid);
+		goto found_result;
+	}
+	if (!remote) {
+		/* result == local commit */
+		oidcpy(result_oid, &local_oid);
+		goto found_result;
+	}
+	assert(local && remote);
+
+	/* Find merge bases */
+	bases = get_merge_bases(local, remote);
+	if (!bases) {
+		base_oid = &null_oid;
+		base_tree_oid = the_hash_algo->empty_tree;
+		if (o->verbosity >= 4)
+			printf("No merge base found; doing history-less merge\n");
+	} else if (!bases->next) {
+		base_oid = &bases->item->object.oid;
+		base_tree_oid = get_commit_tree_oid(bases->item);
+		if (o->verbosity >= 4)
+			printf("One merge base found (%.7s)\n",
+			       oid_to_hex(base_oid));
+	} else {
+		/* TODO: How to handle multiple merge-bases? */
+		base_oid = &bases->item->object.oid;
+		base_tree_oid = get_commit_tree_oid(bases->item);
+		if (o->verbosity >= 3)
+			printf("Multiple merge bases found. Using the first "
+				"(%.7s)\n", oid_to_hex(base_oid));
+	}
+
+	if (o->verbosity >= 4)
+		printf("Merging remote commit %.7s into local commit %.7s with "
+			"merge-base %.7s\n", oid_to_hex(&remote->object.oid),
+			oid_to_hex(&local->object.oid),
+			oid_to_hex(base_oid));
+
+	if (oideq(&remote->object.oid, base_oid)) {
+		/* Already merged; result == local commit */
+		if (o->verbosity >= 2)
+			printf("Already up to date!\n");
+		oidcpy(result_oid, &local->object.oid);
+		goto found_result;
+	}
+	if (oideq(&local->object.oid, base_oid)) {
+		/* Fast-forward; result == remote commit */
+		if (o->verbosity >= 2)
+			printf("Fast-forward\n");
+		oidcpy(result_oid, &remote->object.oid);
+		goto found_result;
+	}
+
+	result = merge_from_diffs(o, base_tree_oid,
+				  get_commit_tree_oid(local),
+				  get_commit_tree_oid(remote), local_tree);
+
+	if (result != 0) { /* non-trivial merge (with or without conflicts) */
+		/* Commit (partial) result */
+		struct commit_list *parents = NULL;
+		commit_list_insert(remote, &parents); /* LIFO order */
+		commit_list_insert(local, &parents);
+		create_notes_commit(o->repo, local_tree, parents, o->commit_msg.buf,
+				    o->commit_msg.len, result_oid);
+	}
+
+found_result:
+	free_commit_list(bases);
+	strbuf_release(&(o->commit_msg));
+	trace_printf("notes_merge(): result = %i, result_oid = %.7s\n",
+	       result, oid_to_hex(result_oid));
+	return result;
+}
+
+int notes_merge_commit(struct notes_merge_options *o,
+		       struct notes_tree *partial_tree,
+		       struct commit *partial_commit,
+		       struct object_id *result_oid)
+{
+	/*
+	 * Iterate through files in .git/NOTES_MERGE_WORKTREE and add all
+	 * found notes to 'partial_tree'. Write the updated 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 OID into 'result_oid'.
+	 */
+	DIR *dir;
+	struct dirent *e;
+	struct strbuf path = STRBUF_INIT;
+	const char *buffer = get_commit_buffer(partial_commit, NULL);
+	const char *msg = strstr(buffer, "\n\n");
+	int baselen;
+
+	git_path_buf(&path, NOTES_MERGE_WORKTREE);
+	if (o->verbosity >= 3)
+		printf("Committing notes in notes merge worktree at %s\n",
+			path.buf);
+
+	if (!msg || msg[2] == '\0')
+		die("partial notes commit has empty message");
+	msg += 2;
+
+	dir = opendir(path.buf);
+	if (!dir)
+		die_errno("could not open %s", path.buf);
+
+	strbuf_addch(&path, '/');
+	baselen = path.len;
+	while ((e = readdir(dir)) != NULL) {
+		struct stat st;
+		struct object_id obj_oid, blob_oid;
+
+		if (is_dot_or_dotdot(e->d_name))
+			continue;
+
+		if (get_oid_hex(e->d_name, &obj_oid)) {
+			if (o->verbosity >= 3)
+				printf("Skipping non-SHA1 entry '%s%s'\n",
+					path.buf, e->d_name);
+			continue;
+		}
+
+		strbuf_addstr(&path, e->d_name);
+		/* write file as blob, and add to partial_tree */
+		if (stat(path.buf, &st))
+			die_errno("Failed to stat '%s'", path.buf);
+		if (index_path(o->repo->index, &blob_oid, path.buf, &st, HASH_WRITE_OBJECT))
+			die("Failed to write blob object from '%s'", path.buf);
+		if (add_note(partial_tree, &obj_oid, &blob_oid, NULL))
+			die("Failed to add resolved note '%s' to notes tree",
+			    path.buf);
+		if (o->verbosity >= 4)
+			printf("Added resolved note for object %s: %s\n",
+				oid_to_hex(&obj_oid), oid_to_hex(&blob_oid));
+		strbuf_setlen(&path, baselen);
+	}
+
+	create_notes_commit(o->repo, partial_tree, partial_commit->parents, msg,
+			    strlen(msg), result_oid);
+	unuse_commit_buffer(partial_commit, buffer);
+	if (o->verbosity >= 4)
+		printf("Finalized notes merge commit: %s\n",
+			oid_to_hex(result_oid));
+	strbuf_release(&path);
+	closedir(dir);
+	return 0;
+}
+
+int notes_merge_abort(struct notes_merge_options *o)
+{
+	/*
+	 * Remove all files within .git/NOTES_MERGE_WORKTREE. We do not remove
+	 * the .git/NOTES_MERGE_WORKTREE directory itself, since it might be
+	 * the current working directory of the user.
+	 */
+	struct strbuf buf = STRBUF_INIT;
+	int ret;
+
+	git_path_buf(&buf, NOTES_MERGE_WORKTREE);
+	if (o->verbosity >= 3)
+		printf("Removing notes merge worktree at %s/*\n", buf.buf);
+	ret = remove_dir_recursively(&buf, REMOVE_DIR_KEEP_TOPLEVEL);
+	strbuf_release(&buf);
+	return ret;
+}