docs: def get_git_tag(self, sha):
          """
          :calls: `GET /repos/:owner/:repo/git/tags/:sha <http://developer.github.com/v3/git/tags>`_
          :param sha: string
          :rtype: :class:`github.GitTag.GitTag`
          """
          assert isinstance(sha, (str, unicode)), sha
          headers, data = self._requester.requestJsonAndCheck(
              "GET",
              self.url + "/git/tags/" + sha
          )
          return github.GitTag.GitTag(self._requester, headers, data, completed=True)