def __get_cs_or_redirect(self, rev, repo, redirect_after=True,

                             partial=False):

        """

        Safe way to get changeset if error occur it redirects to changeset with

        proper message. If partial is set then don't do redirect raise Exception

        instead

        :param rev: revision to fetch

        :param repo: repo instance

        """

        try:

            type_, rev = rev

            return repo.scm_instance.get_changeset(rev)

        except EmptyRepositoryError, e:

            if not redirect_after:

                return None

            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('repo', org_repo)

        incoming_changesets = str2bool(request.GET.get('bundle', False))

        c.fulldiff = fulldiff = request.GET.get('fulldiff')

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

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

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

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

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

              repo=org_repo, as_form=request.GET.get('as_form'),

              bundle=incoming_changesets)

        c.org_repo = org_repo = Repository.get_by_repo_name(org_repo)

        c.other_repo = other_repo = Repository.get_by_repo_name(other_repo)

            raise HTTPNotFound

        if c.org_repo != c.other_repo and h.is_git(c.rhodecode_repo):

            log.error('compare of two remote repos not available for GIT REPOS')

            raise HTTPNotFound

        if c.org_repo.scm_instance.alias != c.other_repo.scm_instance.alias:

            log.error('compare of two different kind of remote repos not available')

            raise HTTPNotFound

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

        self.__get_cs_or_redirect(rev=org_ref, repo=org_repo, partial=partial)

        self.__get_cs_or_redirect(rev=other_ref, repo=other_repo, partial=partial)

        if rev_start and rev_end:

            #replace our org_ref with given CS

            org_ref = ('rev', rev_start)

            other_ref = ('rev', rev_end)

        c.cs_ranges, discovery_data = PullRequestModel().get_compare_data(

                                    org_repo, org_ref, other_repo, other_ref,

                                    )

        c.statuses = c.rhodecode_db_repo.statuses([x.raw_id for x in

                                                   c.cs_ranges])

        c.target_repo = c.repo_name

        # defines that we need hidden inputs with changesets

        c.as_form = request.GET.get('as_form', False)

        if partial:

            return render('compare/compare_cs.html')

        c.org_ref = org_ref[1]

        c.other_ref = other_ref[1]

        if not incoming_changesets and c.cs_ranges and c.org_repo != c.other_repo:

            # case we want a simple diff without incoming changesets, just

            # for review purposes. Make the diff on the forked repo, with

            # revision that is common ancestor

            _org_ref = org_ref

            org_ref = ('rev', getattr(c.cs_ranges[0].parents[0]

                                      if c.cs_ranges[0].parents

                                      else EmptyChangeset(), 'raw_id'))

            log.debug('Changed org_ref from %s to %s' % (_org_ref, org_ref))

            other_repo = org_repo

        diff_limit = self.cut_off_limit if not fulldiff else None

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