docs: def get_git_ref(self, ref):
          """
          :calls: `GET /repos/:owner/:repo/git/refs/:ref <http://developer.github.com/v3/git/refs>`_
          :param ref: string
          :rtype: :class:`github.GitRef.GitRef`
          """
          prefix = "/git/refs/"
          if not self._requester.FIX_REPO_GET_GIT_REF:
              prefix = "/git/"
          assert isinstance(ref, (str, unicode)), ref
          headers, data = self._requester.requestJsonAndCheck(
              "GET",
              self.url + prefix + ref
          )
          return github.GitRef.GitRef(self._requester, headers, data, completed=True)