How to use the kas.repos.Repo function in kas

Checks if path is under version control and returns its root path.
        """
        (ret, output) = run_cmd(['git', 'rev-parse', '--show-toplevel'],
                                cwd=path, fail=False, liveupdate=False)
        if ret == 0:
            return output.strip()

        (ret, output) = run_cmd(['hg', 'root'],
                                cwd=path, fail=False, liveupdate=False)
        if ret == 0:
            return output.strip()

        return path if fallback else None


class RepoImpl(Repo):
    """
        Provides a generic implementation for a Repo.
    """

    async def fetch_async(self):
        """
            Starts asynchronous repository fetch.
        """
        if self.operations_disabled:
            return 0

        if not os.path.exists(self.path):
            os.makedirs(os.path.dirname(self.path), exist_ok=True)
            sdir = os.path.join(get_context().kas_repo_ref_dir or '',
                                self.qualified_name)
            logging.debug('Looking for repo ref dir in %s', sdir)