start_pos = 0

        end_pos = len(revs)

        if start:

            _start = self._get_revision(start)

            try:

                start_pos = revs.index(_start)

            except ValueError:

                pass

        if end is not None:

            _end = self._get_revision(end)

            try:

                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.

        :param ignore_whitespace: If set to ``True``, would not show whitespace

          changes. Defaults to ``False``.

        :param context: How many lines before/after changed lines should be

          shown. Defaults to ``3``. Due to limitations in Git, if

          value passed-in is greater than ``2**31-1``

          (``2147483647``), it will be set to ``2147483647``

          instead. If negative value is passed-in, it will be set to

          ``0`` instead.

        """

        # Git internally uses a signed long int for storing context

        # size (number of lines to show before and after the

            end_pos += 1

        # filter branches

        filter_ = []

        if branch_name:

            filter_.append('branch("%s")' % safe_str(branch_name))

        if start_date:

            filter_.append('date(">%s")' % start_date)

        if end_date:

            filter_.append('date("<%s")' % end_date)

        if filter_ or max_revisions:

            if filter_:

                revspec = ' and '.join(filter_)

            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

            exchange.pull(self._repo, other, heads=None, force=None)

        except ImportError:

            self._repo.pull(other, heads=None, force=None)

        except Abort as err:

            # Propagate error but with vcs's type

            raise RepositoryError(str(err))

    @LazyProperty

    def workdir(self):

        """

        Returns ``Workdir`` instance for this repository.

        """