Function update

builtin/receive-pack.c:1497–1675

}

static const char *update(struct command *cmd, struct shallow_info *si)
{
	const char *name = cmd->ref_name;
	struct strbuf namespaced_name_buf = STRBUF_INIT;
	static char *namespaced_name;
	const char *ret;
	struct object_id *old_oid = &cmd->old_oid;
	struct object_id *new_oid = &cmd->new_oid;
	int do_update_worktree = 0;
	struct worktree **worktrees = get_worktrees();
	const struct worktree *worktree =
		find_shared_symref(worktrees, "HEAD", name);

	/* only refs/... are allowed */
	if (!starts_with(name, "refs/") ||
	    check_refname_format(name + 5, is_null_oid(new_oid) ?
				 REFNAME_ALLOW_ONELEVEL : 0)) {
		rp_error("refusing to update funny ref '%s' remotely", name);
		ret = "funny refname";
		goto out;
	}

	strbuf_addf(&namespaced_name_buf, "%s%s", get_git_namespace(), name);
	free(namespaced_name);
	namespaced_name = strbuf_detach(&namespaced_name_buf, NULL);

	if (worktree && !worktree->is_bare) {
		switch (deny_current_branch) {
		case DENY_IGNORE:
			break;
		case DENY_WARN:
			rp_warning("updating the current branch");
			break;
		case DENY_REFUSE:
		case DENY_UNCONFIGURED:
			rp_error("refusing to update checked out branch: %s", name);
			if (deny_current_branch == DENY_UNCONFIGURED)
				refuse_unconfigured_deny();
			ret = "branch is currently checked out";
			goto out;
		case DENY_UPDATE_INSTEAD:
			/* pass -- let other checks intervene first */
			do_update_worktree = 1;
			break;
		}
	}

	if (!is_null_oid(new_oid) &&
	    !odb_has_object(the_repository->objects, new_oid,
			    ODB_HAS_OBJECT_RECHECK_PACKED | ODB_HAS_OBJECT_FETCH_PROMISOR)) {
		error("unpack should have generated %s, "
		      "but I can't find it!", oid_to_hex(new_oid));
		ret = "bad pack";
		goto out;
	}

	if (!is_null_oid(old_oid) && is_null_oid(new_oid)) {
		if (deny_deletes && starts_with(name, "refs/heads/")) {