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 get_revision(cls, location, rev=None):
        if rev is None:
            rev = 'HEAD'
        current_rev = cls.run_command(
            ['rev-parse', rev],
            show_stdout=False,
            stdout_only=True,
            cwd=location,
        )
        return current_rev.strip()