def get_last_tid(self):
        try:
            spec = {'tid': {'$gt': 0}}
            sort = [('tid', -1)]
            row = self.db.docs.find_one(spec, sort=sort)
        except Exception as e:
            raise DatabaseException(e)
        if row:
            return row['tid']
        return 0
def mkhead(repo: 'Repo', path: PathLike) -> 'Head':
    """:return: New branch/head instance"""
    return git.Head(repo, git.Head.to_full_path(path))