pull_request = db.PullRequest.get_or_404(pull_request_id)

        if pull_request.is_closed():

            raise HTTPForbidden()

        assert pull_request.other_repo.repo_name == repo_name

        # only owner or admin can update it

        owner = pull_request.owner_id == request.authuser.user_id

        repo_admin = auth.HasRepoPermissionLevel('admin')(c.repo_name)

        if not (auth.HasPermissionAny('hg.admin')() or repo_admin or owner):

            raise HTTPForbidden()

        _form = PullRequestPostForm()().to_python(request.POST)

        cur_reviewers = set(pull_request.get_reviewer_users())

        new_reviewers = set(_get_reviewer(s) for s in _form['review_members'])

        old_reviewers = set(_get_reviewer(s) for s in _form['org_review_members'])

        other_added = cur_reviewers - old_reviewers

        other_removed = old_reviewers - cur_reviewers

        if other_added:

            webutils.flash(_('Meanwhile, the following reviewers have been added: %s') %

                    (', '.join(u.username for u in other_added)),

                    category='warning')

        if other_removed:

            webutils.flash(_('Meanwhile, the following reviewers have been removed: %s') %

                    (', '.join(u.username for u in other_removed)),

                    category='warning')

        if _form['updaterev']:

            return self.create_new_iteration(pull_request,

                                      _form['updaterev'],

                                      _form['pullrequest_title'],

                                      _form['pullrequest_desc'],

                                      new_reviewers)

        added_reviewers = new_reviewers - old_reviewers - cur_reviewers

        removed_reviewers = (old_reviewers - new_reviewers) & cur_reviewers

        old_description = pull_request.description

        pull_request.title = _form['pullrequest_title']

        pull_request.description = _form['pullrequest_desc'].strip() or _('No description')

        pull_request.owner = db.User.get_by_username(_form['owner'])

        user = db.User.get(request.authuser.user_id)

        PullRequestModel().mention_from_description(user, pull_request, old_description)

        PullRequestModel().add_reviewers(user, pull_request, added_reviewers)

        PullRequestModel().remove_reviewers(user, pull_request, removed_reviewers)

        meta.Session().commit()

        webutils.flash(_('Pull request updated'), category='success')

        raise HTTPFound(location=pull_request.url())

    @LoginRequired()

    @HasRepoPermissionLevelDecorator('read')

    @base.jsonify

    def delete(self, repo_name, pull_request_id):

        pull_request = db.PullRequest.get_or_404(pull_request_id)

        # only owner can delete it !

        if pull_request.owner_id == request.authuser.user_id:

            PullRequestModel().delete(pull_request)

            meta.Session().commit()

            webutils.flash(_('Successfully deleted pull request'),

                    category='success')

            raise HTTPFound(location=url('my_pullrequests'))

        raise HTTPForbidden()

    @LoginRequired(allow_default_user=True)

    @HasRepoPermissionLevelDecorator('read')

    def show(self, repo_name, pull_request_id, extra=None):

        c.pull_request = db.PullRequest.get_or_404(pull_request_id)

        c.allowed_to_change_status = self._is_allowed_to_change_status(c.pull_request)

        cc_model = ChangesetCommentsModel()

        cs_model = ChangesetStatusModel()

        # pull_requests repo_name we opened it against

        # ie. other_repo must match

        if repo_name != c.pull_request.other_repo.repo_name:

            raise HTTPNotFound

        # load compare data into template context

        c.cs_repo = c.pull_request.org_repo

        (c.cs_ref_type,

         c.cs_ref_name,

         c.cs_rev) = c.pull_request.org_ref.split(':')

        c.a_repo = c.pull_request.other_repo

        (c.a_ref_type,

         c.a_ref_name,

         c.a_rev) = c.pull_request.other_ref.split(':') # a_rev is ancestor

        org_scm_instance = c.cs_repo.scm_instance # property with expensive cache invalidation check!!!

        c.cs_ranges = []

        for x in c.pull_request.revisions:

            try:

                c.cs_ranges.append(org_scm_instance.get_changeset(x))

            except ChangesetDoesNotExistError:

                c.cs_ranges = []

                webutils.flash(_('Revision %s not found in %s') % (x, c.cs_repo.repo_name),

                    'error')

                break

        c.cs_ranges_org = None # not stored and not important and moving target - could be calculated ...

        revs = [ctx.revision for ctx in reversed(c.cs_ranges)]

        c.jsdata = graph_data(org_scm_instance, revs)

        c.is_range = False

        try:

            if c.a_ref_type == 'rev': # this looks like a free range where target is ancestor

                cs_a = org_scm_instance.get_changeset(c.a_rev)

                root_parents = c.cs_ranges[0].parents

                c.is_range = cs_a in root_parents

                #c.merge_root = len(root_parents) > 1 # a range starting with a merge might deserve a warning

        except ChangesetDoesNotExistError: # probably because c.a_rev not found

            pass

        except IndexError: # probably because c.cs_ranges is empty, probably because revisions are missing

            pass

        rev_limit = safe_int(kallithea.CONFIG.get('next_iteration_rev_limit'), 0)

        avail_revs = set()

        avail_show = []

        c.cs_branch_name = c.cs_ref_name

        c.a_branch_name = None

        other_scm_instance = c.a_repo.scm_instance

        c.update_msg = ""

        c.update_msg_other = ""

        try:

            if not c.cs_ranges:

                c.update_msg = _('Error: changesets not found when displaying pull request from %s.') % c.cs_rev

            elif 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

                if not c.is_range and other_scm_instance._repo.revs('present(%s)::&%s', c.cs_ranges[-1].raw_id, c.a_branch_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

                            # - both for avail_revs and for revset results

                            hgrepo = mercurial.unionrepo.makeunionrepository(org_scm_instance.baseui,

                                                                   safe_bytes(org_scm_instance.path),

                                                                   safe_bytes(other_scm_instance.path))

                        else:

                            hgrepo = org_scm_instance._repo

                        show = set(hgrepo.revs('::%ld & !::parents(%s) & !::%s',

                                               avail_revs, revs[0], targethead))

                        if show:

                            c.update_msg = _('The following additional changes are available on %s:') % c.cs_branch_name

                        else:

                            c.update_msg = _('No additional changesets found for iterating on this pull request.')

                    else:

                        show = set()

                        avail_revs = set() # drop revs[0]

                        c.update_msg = _('No additional changesets found for iterating on this pull request.')

                    # TODO: handle branch heads that not are tip-most

                    brevs = org_scm_instance._repo.revs('%s - %ld - %s', c.cs_branch_name, avail_revs, revs[0])

                    if brevs:

                        # also show changesets that are on branch but neither ancestors nor descendants

                        show.update(org_scm_instance._repo.revs('::%ld - ::%ld - ::%s', brevs, avail_revs, c.a_branch_name))

                        show.add(revs[0]) # make sure graph shows this so we can see how they relate

                        c.update_msg_other = _('Note: Branch %s has another head: %s.') % (c.cs_branch_name,

                            org_scm_instance.get_changeset(max(brevs)).short_id)

                    avail_show = sorted(show, reverse=True)

            elif org_scm_instance.alias == 'git':

                c.cs_repo.scm_instance.get_changeset(c.cs_rev) # check it exists - raise ChangesetDoesNotExistError if not

                c.update_msg = _("Git pull requests don't support iterating yet.")

        except ChangesetDoesNotExistError:

            c.update_msg = _('Error: some changesets not found when displaying pull request from %s.') % c.cs_rev

        if rev_limit:

            if len(avail_revs) - 1 > rev_limit:

                c.update_msg = _('%d additional changesets are not shown.') % (len(avail_revs) - 1)

                avail_show = []

        c.avail_revs = avail_revs

        c.avail_cs = [org_scm_instance.get_changeset(r) for r in avail_show]

        c.avail_jsdata = graph_data(org_scm_instance, avail_show)

        raw_ids = [x.raw_id for x in c.cs_ranges]

        c.cs_comments = c.cs_repo.get_comments(raw_ids)

        c.cs_statuses = c.cs_repo.statuses(raw_ids)

        ignore_whitespace_diff = h.get_ignore_whitespace_diff(request.GET)

        diff_context_size = h.get_diff_context_size(request.GET)

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

        diff_limit = None if fulldiff else self.cut_off_limit

        # we swap org/other ref since we run a simple diff on one repo

        log.debug('running diff between %s and %s in %s',

                  c.a_rev, c.cs_rev, org_scm_instance.path)

        try:

            raw_diff = diffs.get_diff(org_scm_instance, rev1=c.a_rev, rev2=c.cs_rev,

                                      ignore_whitespace=ignore_whitespace_diff, context=diff_context_size)

        except ChangesetDoesNotExistError:

            raw_diff = safe_bytes(_("The diff can't be shown - the PR revisions could not be found."))

        diff_processor = diffs.DiffProcessor(raw_diff, diff_limit=diff_limit)

        c.limited_diff = diff_processor.limited_diff

        c.file_diff_data = []

        c.lines_added = 0

        c.lines_deleted = 0

        for f in diff_processor.parsed:

            st = f['stats']

            c.lines_added += st['added']

            c.lines_deleted += st['deleted']

            filename = f['filename']

            fid = h.FID('', filename)

            html_diff = diffs.as_html(parsed_lines=[f])

            c.file_diff_data.append((fid, None, f['operation'], f['old_filename'], filename, html_diff, st))

        # inline comments

        c.inline_cnt = 0

        c.inline_comments = cc_model.get_inline_comments(

                                c.db_repo.repo_id,

                                pull_request=pull_request_id)

        # count inline comments

        for __, lines in c.inline_comments:

            for comments in lines.values():

                c.inline_cnt += len(comments)

        # comments

        c.comments = cc_model.get_comments(c.db_repo.repo_id, pull_request=pull_request_id)

        # (badly named) pull-request status calculation based on reviewer votes

        (c.pull_request_reviewers,

         c.pull_request_pending_reviewers,

         c.current_voting_result,

         ) = cs_model.calculate_pull_request_result(c.pull_request)

        c.changeset_statuses = db.ChangesetStatus.STATUSES

        c.is_ajax_preview = False

        c.ancestors = None # [c.a_rev] ... but that is shown in an other way

        return base.render('/pullrequests/pullrequest_show.html')

    @LoginRequired()

    @HasRepoPermissionLevelDecorator('read')

    @base.jsonify

    def comment(self, repo_name, pull_request_id):

        pull_request = db.PullRequest.get_or_404(pull_request_id)

        allowed_to_change_status = self._is_allowed_to_change_status(pull_request)

        return create_cs_pr_comment(repo_name, pull_request=pull_request,

                allowed_to_change_status=allowed_to_change_status)

    @LoginRequired()

    @HasRepoPermissionLevelDecorator('read')

    @base.jsonify

    def delete_comment(self, repo_name, comment_id):

        return delete_cs_pr_comment(repo_name, comment_id)