Function stat_branch_pair

remote.c:2190–2253

 */

static int stat_branch_pair(const char *branch_name, const char *base,
			     int *num_ours, int *num_theirs,
			     enum ahead_behind_flags abf)
{
	struct object_id oid;
	struct commit *ours, *theirs;
	struct rev_info revs;
	struct strvec argv = STRVEC_INIT;

	/* Cannot stat if what we used to build on no longer exists */
	if (refs_read_ref(get_main_ref_store(the_repository), base, &oid))
		return -1;
	theirs = lookup_commit_reference(the_repository, &oid);
	if (!theirs)
		return -1;

	if (refs_read_ref(get_main_ref_store(the_repository), branch_name, &oid))
		return -1;
	ours = lookup_commit_reference(the_repository, &oid);
	if (!ours)
		return -1;

	*num_theirs = *num_ours = 0;

	/* are we the same? */
	if (theirs == ours)
		return 0;
	if (abf == AHEAD_BEHIND_QUICK)
		return 1;
	if (abf != AHEAD_BEHIND_FULL)
		BUG("stat_branch_pair: invalid abf '%d'", abf);

	/* Run "rev-list --left-right ours...theirs" internally... */
	strvec_push(&argv, ""); /* ignored */
	strvec_push(&argv, "--left-right");
	strvec_pushf(&argv, "%s...%s",
		     oid_to_hex(&ours->object.oid),
		     oid_to_hex(&theirs->object.oid));
	strvec_push(&argv, "--");

	repo_init_revisions(the_repository, &revs, NULL);
	setup_revisions_from_strvec(&argv, &revs, NULL);
	if (prepare_revision_walk(&revs))
		die(_("revision walk setup failed"));

	/* ... and count the commits on each side. */
	while (1) {
		struct commit *c = get_revision(&revs);
		if (!c)
			break;
		if (c->object.flags & SYMMETRIC_LEFT)
			(*num_ours)++;
		else
			(*num_theirs)++;
	}

	/* clear object flags smudged by the above traversal */
	clear_commit_marks(ours, ALL_REV_FLAGS);