if org_scm_instance.alias == 'hg' and c.a_ref_name != 'ancestor':

            if c.cs_ref_type != 'branch':

                c.cs_branch_name = org_scm_instance.get_changeset(c.cs_ref_name).branch # use ref_type ?

            c.a_branch_name = c.a_ref_name

            if c.a_ref_type != 'branch':

                try:

                    c.a_branch_name = other_scm_instance.get_changeset(c.a_ref_name).branch # use ref_type ?

                except EmptyRepositoryError:

                    c.a_branch_name = 'null' # not a branch name ... but close enough

            # candidates: descendants of old head that are on the right branch

            #             and not are the old head itself ...

            #             and nothing at all if old head is a descendant of target ref name

                c.update_msg = _('This pull request has already been merged to %s.') % c.a_branch_name

            elif c.pull_request.is_closed():

                c.update_msg = _('This pull request has been closed and can not be updated.')

            else: # look for descendants of PR head on source branch in org repo

                avail_revs = org_scm_instance._repo.revs('%s:: & branch(%s)',

                                                         revs[0], c.cs_branch_name)

                if len(avail_revs) > 1: # more than just revs[0]

                    # also show changesets that not are descendants but would be merged in

                    targethead = other_scm_instance.get_changeset(c.a_branch_name).raw_id

                    if org_scm_instance.path != other_scm_instance.path:

                        # Note: org_scm_instance.path must come first so all

                        # valid revision numbers are 100% org_scm compatible