def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def rel(self, f):
        """Convert repo path back to path that is relative to cwd of matcher."""
        return util.pathto(self._root, self._cwd, f)