int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
{
	char *last_branch = substitute_branch_name(&str, &len);
	const char **p;
	int logs_found = 0;
	struct strbuf path = STRBUF_INIT;

	*log = NULL;
	for (p = ref_rev_parse_rules; *p; p++) {
		unsigned char hash[20];
		const char *ref, *it;

		strbuf_reset(&path);
		strbuf_addf(&path, *p, len, str);
		ref = resolve_ref_unsafe(path.buf, RESOLVE_REF_READING,
					 hash, NULL);
		if (!ref)
			continue;
		if (reflog_exists(path.buf))
			it = path.buf;
		else if (strcmp(ref, path.buf) && reflog_exists(ref))
			it = ref;
		else
			continue;
		if (!logs_found++) {
			*log = xstrdup(it);
			hashcpy(sha1, hash);
		}
		if (!warn_ambiguous_refs)
			break;
	}
	strbuf_release(&path);
	free(last_branch);
	return logs_found;
}

int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
{
	char *last_branch = substitute_branch_name(&str, &len);
	const char **p;
	int logs_found = 0;

	*log = NULL;
	for (p = ref_rev_parse_rules; *p; p++) {
		unsigned char hash[20];
		char path[PATH_MAX];
		const char *ref, *it;

		mksnpath(path, sizeof(path), *p, len, str);
		ref = resolve_ref_unsafe(path, RESOLVE_REF_READING,
					 hash, NULL);
		if (!ref)
			continue;
		if (reflog_exists(path))
			it = path;
		else if (strcmp(ref, path) && reflog_exists(ref))
			it = ref;
		else
			continue;
		if (!logs_found++) {
			*log = xstrdup(it);
			hashcpy(sha1, hash);
		}
		if (!warn_ambiguous_refs)
			break;
	}
	free(last_branch);
	return logs_found;
}

static int fsck_head_link(void)
{
	int null_is_error = 0;

	if (verbose)
		fprintf(stderr, "Checking HEAD link\n");

	head_points_at = resolve_ref_unsafe("HEAD", 0, &head_oid, NULL);
	if (!head_points_at) {
		errors_found |= ERROR_REFS;
		return error("Invalid HEAD");
	}
	if (!strcmp(head_points_at, "HEAD"))
		/* detached HEAD */
		null_is_error = 1;
	else if (!starts_with(head_points_at, "refs/heads/")) {
		errors_found |= ERROR_REFS;
		return error("HEAD points to something strange (%s)",
			     head_points_at);
	}
	if (is_null_oid(&head_oid)) {
		if (null_is_error) {
			errors_found |= ERROR_REFS;
			return error("HEAD: detached HEAD points at nothing");
		}
		fprintf(stderr, "notice: HEAD points to an unborn branch (%s)\n",
			head_points_at + 11);
	}
	return 0;
}

static char *get_default_remote(void)
{
	char *dest = NULL, *ret;
	unsigned char sha1[20];
	struct strbuf sb = STRBUF_INIT;
	const char *refname = resolve_ref_unsafe("HEAD", 0, sha1, NULL);

	if (!refname)
		die(_("No such ref: %s"), "HEAD");

	/* detached HEAD */
	if (!strcmp(refname, "HEAD"))
		return xstrdup("origin");

	if (!skip_prefix(refname, "refs/heads/", &refname))
		die(_("Expecting a full ref name, got %s"), refname);

	strbuf_addf(&sb, "branch.%s.remote", refname);
	if (git_config_get_string(sb.buf, &dest))
		ret = xstrdup("origin");
	else
		ret = dest;

	strbuf_release(&sb);
	return ret;
}

int expand_ref(const char *str, int len, unsigned char *sha1, char **ref)
{
	const char **p, *r;
	int refs_found = 0;
	struct strbuf fullref = STRBUF_INIT;

	*ref = NULL;
	for (p = ref_rev_parse_rules; *p; p++) {
		unsigned char sha1_from_ref[20];
		unsigned char *this_result;
		int flag;

		this_result = refs_found ? sha1_from_ref : sha1;
		strbuf_reset(&fullref);
		strbuf_addf(&fullref, *p, len, str);
		r = resolve_ref_unsafe(fullref.buf, RESOLVE_REF_READING,
				       this_result, &flag);
		if (r) {
			if (!refs_found++)
				*ref = xstrdup(r);
			if (!warn_ambiguous_refs)
				break;
		} else if ((flag & REF_ISSYMREF) && strcmp(fullref.buf, "HEAD")) {
			warning("ignoring dangling symref %s.", fullref.buf);
		} else if ((flag & REF_ISBROKEN) && strchr(fullref.buf, '/')) {
			warning("ignoring broken ref %s.", fullref.buf);
		}
	}
	strbuf_release(&fullref);
	return refs_found;
}

static int is_index_unchanged(void)
{
	unsigned char head_sha1[20];
	struct commit *head_commit;

	if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, head_sha1, NULL))
		return error(_("Could not resolve HEAD commit\n"));

	head_commit = lookup_commit(head_sha1);

	/*
	 * If head_commit is NULL, check_commit, called from
	 * lookup_commit, would have indicated that head_commit is not
	 * a commit object already.  parse_commit() will return failure
	 * without further complaints in such a case.  Otherwise, if
	 * the commit is invalid, parse_commit() will complain.  So
	 * there is nothing for us to say here.  Just return failure.
	 */
	if (parse_commit(head_commit))
		return -1;

	if (!active_cache_tree)
		active_cache_tree = cache_tree();

	if (!cache_tree_fully_valid(active_cache_tree))
		if (cache_tree_update(&the_index, 0))
			return error(_("Unable to update cache tree\n"));

	return !hashcmp(active_cache_tree->sha1, head_commit->tree->object.oid.hash);
}

static const char *remote_submodule_branch(const char *path)
{
	const struct submodule *sub;
	gitmodules_config();
	git_config(submodule_config, NULL);

	sub = submodule_from_path(null_sha1, path);
	if (!sub)
		return NULL;

	if (!sub->branch)
		return "master";

	if (!strcmp(sub->branch, ".")) {
		unsigned char sha1[20];
		const char *refname = resolve_ref_unsafe("HEAD", 0, sha1, NULL);

		if (!refname)
			die(_("No such ref: %s"), "HEAD");

		/* detached HEAD */
		if (!strcmp(refname, "HEAD"))
			die(_("Submodule (%s) branch configured to inherit "
			      "branch from superproject, but the superproject "
			      "is not on any branch"), sub->name);

		if (!skip_prefix(refname, "refs/heads/", &refname))
			die(_("Expecting a full ref name, got %s"), refname);
		return refname;
	}

	return sub->branch;
}

static char *find_branch_name(struct rev_info *rev)
{
	int i, positive = -1;
	unsigned char branch_sha1[20];
	struct strbuf buf = STRBUF_INIT;
	const char *branch;

	for (i = 0; i < rev->cmdline.nr; i++) {
		if (rev->cmdline.rev[i].flags & UNINTERESTING)
			continue;
		if (positive < 0)
			positive = i;
		else
			return NULL;
	}
	if (positive < 0)
		return NULL;
	strbuf_addf(&buf, "refs/heads/%s", rev->cmdline.rev[positive].name);
	branch = resolve_ref_unsafe(buf.buf, branch_sha1, 1, NULL);
	if (!branch ||
	    prefixcmp(branch, "refs/heads/") ||
	    hashcmp(rev->cmdline.rev[positive].item->sha1, branch_sha1))
		branch = NULL;
	strbuf_release(&buf);
	if (branch)
		return xstrdup(rev->cmdline.rev[positive].name);
	return NULL;
}

/*
 * Do we have HEAD in the output, and also the branch it points at?
 * If so, find that decoration entry for that current branch.
 */
static const struct name_decoration *current_pointed_by_HEAD(const struct name_decoration *decoration)
{
	const struct name_decoration *list, *head = NULL;
	const char *branch_name = NULL;
	unsigned char unused[20];
	int rru_flags;

	/* First find HEAD */
	for (list = decoration; list; list = list->next)
		if (list->type == DECORATION_REF_HEAD) {
			head = list;
			break;
		}
	if (!head)
		return NULL;

	/* Now resolve and find the matching current branch */
	branch_name = resolve_ref_unsafe("HEAD", 0, unused, &rru_flags);
	if (!(rru_flags & REF_ISSYMREF))
		return NULL;

	if (!starts_with(branch_name, "refs/"))
		return NULL;

	/* OK, do we have that ref in the list? */
	for (list = decoration; list; list = list->next)
		if ((list->type == DECORATION_REF_LOCAL) &&
		    !strcmp(branch_name, list->name)) {
			return list;
		}

	return NULL;
}

int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
{
	char *last_branch = substitute_branch_name(&str, &len);
	const char **p, *r;
	int refs_found = 0;

	*ref = NULL;
	for (p = ref_rev_parse_rules; *p; p++) {
		char fullref[PATH_MAX];
		unsigned char sha1_from_ref[20];
		unsigned char *this_result;
		int flag;

		this_result = refs_found ? sha1_from_ref : sha1;
		mksnpath(fullref, sizeof(fullref), *p, len, str);
		r = resolve_ref_unsafe(fullref, RESOLVE_REF_READING,
				       this_result, &flag);
		if (r) {
			if (!refs_found++)
				*ref = xstrdup(r);
			if (!warn_ambiguous_refs)
				break;
		} else if ((flag & REF_ISSYMREF) && strcmp(fullref, "HEAD")) {
			warning("ignoring dangling symref %s.", fullref);
		} else if ((flag & REF_ISBROKEN) && strchr(fullref, '/')) {
			warning("ignoring broken ref %s.", fullref);
		}
	}
	free(last_branch);
	return refs_found;
}

static char *guess_defbranch(void)
{
	const char *ref;
	unsigned char sha1[20];

	ref = resolve_ref_unsafe("HEAD", sha1, 0, NULL);
	if (!ref || prefixcmp(ref, "refs/heads/"))
		return "master";
	return xstrdup(ref + 11);
}

/**
 * Add the head_sha1 and head_ref (if not detached) to the given worktree
 */
static void add_head_info(struct strbuf *head_ref, struct worktree *worktree)
{
	if (head_ref->len) {
		if (worktree->is_detached) {
			get_sha1_hex(head_ref->buf, worktree->head_sha1);
		} else {
			resolve_ref_unsafe(head_ref->buf, 0, worktree->head_sha1, NULL);
			worktree->head_ref = strbuf_detach(head_ref, NULL);
		}
	}
}

static void check_aliased_update(struct command *cmd, struct string_list *list)
{
	struct strbuf buf = STRBUF_INIT;
	const char *dst_name;
	struct string_list_item *item;
	struct command *dst_cmd;
	unsigned char sha1[GIT_SHA1_RAWSZ];
	char cmd_oldh[GIT_SHA1_HEXSZ + 1],
	     cmd_newh[GIT_SHA1_HEXSZ + 1],
	     dst_oldh[GIT_SHA1_HEXSZ + 1],
	     dst_newh[GIT_SHA1_HEXSZ + 1];
	int flag;

	strbuf_addf(&buf, "%s%s", get_git_namespace(), cmd->ref_name);
	dst_name = resolve_ref_unsafe(buf.buf, 0, sha1, &flag);
	strbuf_release(&buf);

	if (!(flag & REF_ISSYMREF))
		return;

	if (!dst_name) {
		rp_error("refusing update to broken symref '%s'", cmd->ref_name);
		cmd->skip_update = 1;
		cmd->error_string = "broken symref";
		return;
	}
	dst_name = strip_namespace(dst_name);

	if ((item = string_list_lookup(list, dst_name)) == NULL)
		return;

	cmd->skip_update = 1;

	dst_cmd = (struct command *) item->util;

	if (!hashcmp(cmd->old_sha1, dst_cmd->old_sha1) &&
	    !hashcmp(cmd->new_sha1, dst_cmd->new_sha1))
		return;

	dst_cmd->skip_update = 1;

	find_unique_abbrev_r(cmd_oldh, cmd->old_sha1, DEFAULT_ABBREV);
	find_unique_abbrev_r(cmd_newh, cmd->new_sha1, DEFAULT_ABBREV);
	find_unique_abbrev_r(dst_oldh, dst_cmd->old_sha1, DEFAULT_ABBREV);
	find_unique_abbrev_r(dst_newh, dst_cmd->new_sha1, DEFAULT_ABBREV);
	rp_error("refusing inconsistent update between symref '%s' (%s..%s) and"
		 " its target '%s' (%s..%s)",
		 cmd->ref_name, cmd_oldh, cmd_newh,
		 dst_cmd->ref_name, dst_oldh, dst_newh);

	cmd->error_string = dst_cmd->error_string =
		"inconsistent aliased update";
}

static char *resolve_symref(const char *src, const char *prefix)
{
	unsigned char sha1[20];
	int flag;
	const char *dst;

	dst = resolve_ref_unsafe(src, sha1, 0, &flag);
	if (!(dst && (flag & REF_ISSYMREF)))
		return NULL;
	if (prefix)
		skip_prefix(dst, prefix, &dst);
	return xstrdup(dst);
}

static int find_symref(const char *refname, const struct object_id *oid,
		       int flag, void *cb_data)
{
	const char *symref_target;
	struct string_list_item *item;

	if ((flag & REF_ISSYMREF) == 0)
		return 0;
	symref_target = resolve_ref_unsafe(refname, 0, NULL, &flag);
	if (!symref_target || (flag & REF_ISSYMREF) == 0)
		die("'%s' is a symref but it is not?", refname);
	item = string_list_append(cb_data, refname);
	item->util = xstrdup(symref_target);
	return 0;
}

static void check_symref(const char *HEAD, int quiet)
{
	unsigned char sha1[20];
	int flag;
	const char *refs_heads_master = resolve_ref_unsafe(HEAD, sha1, 0, &flag);

	if (!refs_heads_master)
		die("No such ref: %s", HEAD);
	else if (!(flag & REF_ISSYMREF)) {
		if (!quiet)
			die("ref %s is not a symbolic ref", HEAD);
		else
			exit(1);
	}
	puts(refs_heads_master);
}

static void set_upstreams(struct transport *transport, struct ref *refs,
	int pretend)
{
	struct ref *ref;
	for (ref = refs; ref; ref = ref->next) {
		const char *localname;
		const char *tmp;
		const char *remotename;
		unsigned char sha[20];
		int flag = 0;
		/*
		 * Check suitability for tracking. Must be successful /
		 * already up-to-date ref create/modify (not delete).
		 */
		if (ref->status != REF_STATUS_OK &&
			ref->status != REF_STATUS_UPTODATE)
			continue;
		if (!ref->peer_ref)
			continue;
		if (is_null_oid(&ref->new_oid))
			continue;

		/* Follow symbolic refs (mainly for HEAD). */
		localname = ref->peer_ref->name;
		remotename = ref->name;
		tmp = resolve_ref_unsafe(localname, RESOLVE_REF_READING,
					 sha, &flag);
		if (tmp && flag & REF_ISSYMREF &&
			starts_with(tmp, "refs/heads/"))
			localname = tmp;

		/* Both source and destination must be local branches. */
		if (!localname || !starts_with(localname, "refs/heads/"))
			continue;
		if (!remotename || !starts_with(remotename, "refs/heads/"))
			continue;

		if (!pretend)
			install_branch_config(BRANCH_CONFIG_VERBOSE,
				localname + 11, transport->remote->name,
				remotename);
		else
			printf(_("Would set upstream of '%s' to '%s' of '%s'\n"),
				localname + 11, remotename + 11,
				transport->remote->name);
	}
}

static int show_head_ref(const char *refname, const unsigned char *sha1,
	int flag, void *cb_data)
{
	struct strbuf *buf = cb_data;

	if (flag & REF_ISSYMREF) {
		unsigned char unused[20];
		const char *target = resolve_ref_unsafe(refname, unused, 1, NULL);
		const char *target_nons = strip_namespace(target);

		strbuf_addf(buf, "ref: %s\n", target_nons);
	} else {
		strbuf_addf(buf, "%s\n", sha1_to_hex(sha1));
	}

	return 0;
}

static int show_head_ref(const char *refname, const struct object_id *oid,
			 int flag, void *cb_data)
{
	struct strbuf *buf = cb_data;

	if (flag & REF_ISSYMREF) {
		const char *target = resolve_ref_unsafe(refname,
							RESOLVE_REF_READING,
							NULL, NULL);

		if (target)
			strbuf_addf(buf, "ref: %s\n", strip_namespace(target));
	} else {
		strbuf_addf(buf, "%s\n", oid_to_hex(oid));
	}

	return 0;
}

static void check_symref(const char *HEAD, int quiet)
{
	unsigned char sha1[20];
	int flag;
	const char *refname = resolve_ref_unsafe(HEAD, sha1, 0, &flag);

	if (!refname)
		die("No such ref: %s", HEAD);
	else if (!(flag & REF_ISSYMREF)) {
		if (!quiet)
			die("ref %s is not a symbolic ref", HEAD);
		else
			exit(1);
	}
	if (shorten)
		refname = shorten_unambiguous_ref(refname, 0);
	puts(refname);
}