selected = n

        tags = []

        for tag, tagrev in repo.tags.iteritems():

            n = 'tag:%s:%s' % (tag, tagrev)

            tags.append((n, tag))

            if rev == tagrev and tag != 'tip':  # tip is not a real tag - and its branch is better

                selected = n

        # prio 1: rev was selected as existing entry above

        # prio 2: create special entry for rev; rev _must_ be used

        specials = []

        if rev and selected is None:

            selected = 'rev:%s:%s' % (rev, rev)

            specials = [(selected, '%s: %s' % (_("Changeset"), rev[:12]))]

        # prio 3: most recent peer branch

        if peers and not selected:

            selected = peers[0][0][0]

        # prio 4: tip revision

        if not selected:

            if h.is_hg(repo):

            else:

                if 'master' in repo.branches:

                    selected = 'branch:master:%s' % repo.branches['master']

                else:

                    k, v = repo.branches.items()[0]

                    selected = 'branch:%s:%s' % (k, v)

        groups = [(specials, _("Special")),

                  (peers, _("Peer branches")),

                  (bookmarks, _("Bookmarks")),

                  (branches, _("Branches")),

                  (tags, _("Tags")),

                  ]

        return [g for g in groups if g[0]], selected

    def _get_is_allowed_change_status(self, pull_request):

        owner = self.authuser.user_id == pull_request.user_id

        reviewer = self.authuser.user_id in [x.user_id for x in

                                                   pull_request.reviewers]

        return self.authuser.admin or owner or reviewer

    def _load_compare_data(self, pull_request, enable_comments=True):

        """

        Load context data needed for generating compare diff