def get_backend_for_dir(self, location):
        # type: (str) -> Optional[VersionControl]
        """
        Return a VersionControl object if a repository of that type is found
        at the given directory.
        """
        vcs_backends = {}
        for vcs_backend in self._registry.values():
            repo_path = vcs_backend.get_repository_root(location)
            if not repo_path:
                continue
            logger.debug('Determine that %s uses VCS: %s',
                         location, vcs_backend.name)
            vcs_backends[repo_path] = vcs_backend

        if not vcs_backends:
            return None

        # Choose the VCS in the inner-most directory. Since all repository
        # roots found here would be either `location` or one of its
        # parents, the longest path should have the most path components,
        # i.e. the backend representing the inner-most repository.
        inner_most_repo_path = max(vcs_backends, key=len)
        return vcs_backends[inner_most_repo_path]

        Return a VersionControl object if a repository of that type is found
        at the given directory.
        
product/gradle-plugin/src/main/python/pip/_internal/vcs/versioncontrol.py