end_pos = revs.index(_end)

            except ValueError:

                pass

        if None not in [start, end] and start_pos > end_pos:

            raise RepositoryError('start cannot be after end')

        if end_pos is not None:

            end_pos += 1

        revs = revs[start_pos:end_pos]

        if reverse:

        return CollectionGenerator(self, revs)

    def get_diff(self, rev1, rev2, path=None, ignore_whitespace=False,

                 context=3):

        """

        Returns (git like) *diff*, as plain text. Shows changes introduced by

        ``rev2`` since ``rev1``.

        :param rev1: Entry point from which diff is shown. Can be

          ``self.EMPTY_CHANGESET`` - in this case, patch showing all

          the changes since empty state of the repository until ``rev2``

        :param rev2: Until which revision changes should be shown.

            else:

                revspec = 'all()'

            if max_revisions:

                revspec = 'limit(%s, %s)' % (revspec, max_revisions)

            revisions = scmutil.revrange(self._repo, [revspec])

        else:

            revisions = self.revisions

        # this is very much a hack to turn this into a list; a better solution

        # would be to get rid of this function entirely and use revsets

        revs = list(revisions)[start_pos:end_pos]

        if reverse:

        return CollectionGenerator(self, revs)

    def pull(self, url):

        """

        Tries to pull changes from external location.

        """

        url = self._get_url(url)

        other = peer(self._repo, {}, url)

        try:

            # hg 3.2 moved push / pull to exchange module

            from mercurial import exchange