:calls: `GET /repos/:owner/:repo/compare/:base...:head <http://developer.github.com/v3/repos/commits>`_
        :param base: string
        :param head: string
        :rtype: :class:`github.Comparison.Comparison`

def compare(self, base, head):
        """
        :calls: `GET /repos/:owner/:repo/compare/:base...:head <http://developer.github.com/v3/repos/commits>`_
        :param base: string
        :param head: string
        :rtype: :class:`github.Comparison.Comparison`
        """
        assert isinstance(base, (str, unicode)), base
        assert isinstance(head, (str, unicode)), head
        headers, data = self._requester.requestJsonAndCheck(
            "GET",
            self.url + "/compare/" + base + "..." + head
        )
        return github.Comparison.Comparison(self._requester, headers, data, completed=True)