h.flash(h.literal(_('There are no changesets yet')),

                    category='warning')

            redirect(url('summary_home', repo_name=repo.repo_name))

        except RepositoryError, e:

            log.error(traceback.format_exc())

            h.flash(str(e), category='warning')

            if not partial:

                redirect(h.url('summary_home', repo_name=repo.repo_name))

            raise HTTPBadRequest()

    def index(self, org_ref_type, org_ref, other_ref_type, other_ref):

        org_repo = c.rhodecode_db_repo.repo_name

        org_ref = (org_ref_type, org_ref)

        other_ref = (other_ref_type, other_ref)

        other_repo = request.GET.get('other_repo', org_repo)

        rev_start = request.GET.get('rev_start')

        rev_end = request.GET.get('rev_end')

        # partial uses compare_cs.html template directly

        partial = request.environ.get('HTTP_X_PARTIAL_XHR')

        # as_form puts hidden input field with changeset revisions

        c.as_form = partial and request.GET.get('as_form')

        # swap url for compare_diff page - never partial and never as_form

        c.swap_url = h.url('compare_url',

            repo_name=other_repo,

            org_ref_type=other_ref[0], org_ref=other_ref[1],

            other_repo=org_repo,

            other_ref_type=org_ref[0], other_ref=org_ref[1])

            return render('compare/compare_cs.html')

        if ancestor and org_repo != other_repo:

            # case we want a simple diff without incoming changesets,

            # previewing what will be merged.

            # Make the diff on the forked repo, with

            # revision that is common ancestor

            log.debug('Using ancestor %s as org_ref instead of %s'

                      % (ancestor, org_ref))

            org_ref = ('rev', ancestor)

            org_repo = other_repo

        _diff = diffs.differ(org_repo, org_ref, other_repo, other_ref)

        diff_processor = diffs.DiffProcessor(_diff or '', format='gitdiff',

                                             diff_limit=diff_limit)

        _parsed = diff_processor.prepare()

        c.limited_diff = False

        if isinstance(_parsed, LimitedDiffContainer):

            c.limited_diff = True

        c.files = []

        :param org_repo:

        :param org_ref:

        :param other_repo:

        :param other_ref:

        """

        if len(org_ref) != 2 or not isinstance(org_ref, (list, tuple)):

            raise Exception('org_ref must be a two element list/tuple')

        if len(other_ref) != 2 or not isinstance(org_ref, (list, tuple)):

            raise Exception('other_ref must be a two element list/tuple')

        return cs_ranges, ancestor