pullrequests: introduce limit to stop displaying additional changes

We've noticed some scalability issues when many descendants exist for the
changesets in a pull request.

To resolve this issue, we instead do not display any additional changes at all
if the amount of additional changes is larger than a configured limit.

(This occurred because we were merging a lot of heads in the repository.)

Throwing away some of the changesets would also keep the total amount more
manageable, but this would result in an (for the user) unpredictable subset of
changesets being shown.

This could be extended further with "too long to be shown - click here to
show", but that was quite a bit of additional work and did not cover our use
case of not allowing the display at all in case of too many additional changes.

kallithea/controllers/pullrequests.py

@@ -1,638 +1,646 b''
 # -*- coding: utf-8 -*-
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation, either version 3 of the License, or
 # (at your option) any later version.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 """
 kallithea.controllers.pullrequests
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 pull requests controller for Kallithea for initializing pull requests
 
 This file was forked by the Kallithea project in July 2014.
 Original author and date, and relevant copyright and licensing information is below:
 :created_on: May 7, 2012
 :author: marcink
 :copyright: (c) 2013 RhodeCode GmbH, and others.
 :license: GPLv3, see LICENSE.md for more details.
 """
 
 import logging
 import traceback
 
 import formencode
 import mercurial.unionrepo
 from tg import request
 from tg import tmpl_context as c
 from tg.i18n import ugettext as _
 from webob.exc import HTTPBadRequest, HTTPForbidden, HTTPFound, HTTPNotFound
 
+import kallithea
 import kallithea.lib.helpers as h
 from kallithea.controllers import base
 from kallithea.controllers.changeset import create_cs_pr_comment, delete_cs_pr_comment
 from kallithea.lib import auth, diffs, webutils
 from kallithea.lib.auth import HasRepoPermissionLevelDecorator, LoginRequired
 from kallithea.lib.graphmod import graph_data
 from kallithea.lib.page import Page
 from kallithea.lib.utils2 import ascii_bytes, safe_bytes, safe_int
 from kallithea.lib.vcs.exceptions import ChangesetDoesNotExistError, EmptyRepositoryError
 from kallithea.lib.webutils import url
 from kallithea.model import db, meta
 from kallithea.model.changeset_status import ChangesetStatusModel
 from kallithea.model.comment import ChangesetCommentsModel
 from kallithea.model.forms import PullRequestForm, PullRequestPostForm
 from kallithea.model.pull_request import CreatePullRequestAction, CreatePullRequestIterationAction, PullRequestModel
 
 
 log = logging.getLogger(__name__)
 
 
 def _get_reviewer(user_id):
     """Look up user by ID and validate it as a potential reviewer."""
     try:
         user = db.User.get(int(user_id))
     except ValueError:
         user = None
 
     if user is None or user.is_default_user:
         webutils.flash(_('Invalid reviewer "%s" specified') % user_id, category='error')
         raise HTTPBadRequest()
 
     return user
 
 
 class PullrequestsController(base.BaseRepoController):
 
     def _get_repo_refs(self, repo, rev=None, branch=None, branch_rev=None):
         """return a structure with scm repo's interesting changesets, suitable for
         the selectors in pullrequest.html
 
         rev: a revision that must be in the list somehow and selected by default
         branch: a branch that must be in the list and selected by default - even if closed
         branch_rev: a revision of which peers should be preferred and available."""
         # list named branches that has been merged to this named branch - it should probably merge back
         peers = []
 
         if branch_rev:
             # a revset not restricting to merge() would be better
             # (especially because it would get the branch point)
             # ... but is currently too expensive
             # including branches of children could be nice too
             peerbranches = set()
             for i in repo._repo.revs(
                 b"sort(parents(branch(id(%s)) and merge()) - branch(id(%s)), -rev)",
                 ascii_bytes(branch_rev), ascii_bytes(branch_rev),
             ):
                 for abranch in repo.get_changeset(i).branches:
                     if abranch not in peerbranches:
                         n = 'branch:%s:%s' % (abranch, repo.get_changeset(abranch).raw_id)
                         peers.append((n, abranch))
                         peerbranches.add(abranch)
 
         selected = None
         tiprev = repo.tags.get('tip')
         tipbranch = None
 
         branches = []
         for abranch, branchrev in repo.branches.items():
             n = 'branch:%s:%s' % (abranch, branchrev)
             desc = abranch
             if branchrev == tiprev:
                 tipbranch = abranch
                 desc = '%s (current tip)' % desc
             branches.append((n, desc))
             if rev == branchrev:
                 selected = n
             if branch == abranch:
                 if not rev:
                     selected = n
                 branch = None
         if branch:  # branch not in list - it is probably closed
             branchrev = repo.closed_branches.get(branch)
             if branchrev:
                 n = 'branch:%s:%s' % (branch, branchrev)
                 branches.append((n, _('%s (closed)') % branch))
                 selected = n
                 branch = None
             if branch:
                 log.debug('branch %r not found in %s', branch, repo)
 
         bookmarks = []
         for bookmark, bookmarkrev in repo.bookmarks.items():
             n = 'book:%s:%s' % (bookmark, bookmarkrev)
             bookmarks.append((n, bookmark))
             if rev == bookmarkrev:
                 selected = n
 
         tags = []
         for tag, tagrev in repo.tags.items():
             if tag == 'tip':
                 continue
             n = 'tag:%s:%s' % (tag, tagrev)
             tags.append((n, tag))
             # note: even if rev == tagrev, don't select the static tag - it must be chosen explicitly
 
         # 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]
 
         # prio 4: tip revision
         if not selected:
             if repo.alias == 'hg':
                 if tipbranch:
                     selected = 'branch:%s:%s' % (tipbranch, tiprev)
                 else:
                     selected = 'tag:null:' + repo.EMPTY_CHANGESET
                     tags.append((selected, 'null'))
             else:  # Git
                 assert repo.alias == 'git'
                 if not repo.branches:
                     selected = ''  # doesn't make sense, but better than nothing
                 elif 'master' in repo.branches:
                     selected = 'branch:master:%s' % repo.branches['master']
                 else:
                     k, v = list(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 _is_allowed_to_change_status(self, pull_request):
         if pull_request.is_closed():
             return False
 
         owner = request.authuser.user_id == pull_request.owner_id
         reviewer = db.PullRequestReviewer.query() \
             .filter(db.PullRequestReviewer.pull_request == pull_request) \
             .filter(db.PullRequestReviewer.user_id == request.authuser.user_id) \
             .count() != 0
 
         return request.authuser.admin or owner or reviewer
 
     @LoginRequired(allow_default_user=True)
     @HasRepoPermissionLevelDecorator('read')
     def show_all(self, repo_name):
         c.from_ = request.GET.get('from_') or ''
         c.closed = request.GET.get('closed') or ''
         url_params = {}
         if c.from_:
             url_params['from_'] = 1
         if c.closed:
             url_params['closed'] = 1
         p = safe_int(request.GET.get('page'), 1)
 
         q = db.PullRequest.query(include_closed=c.closed, sorted=True)
         if c.from_:
             q = q.filter_by(org_repo=c.db_repo)
         else:
             q = q.filter_by(other_repo=c.db_repo)
         c.pull_requests = q.all()
 
         c.pullrequests_pager = Page(c.pull_requests, page=p, items_per_page=100, **url_params)
 
         return base.render('/pullrequests/pullrequest_show_all.html')
 
     @LoginRequired()
     def show_my(self):
         c.closed = request.GET.get('closed') or ''
 
         c.my_pull_requests = db.PullRequest.query(
             include_closed=c.closed,
             sorted=True,
         ).filter_by(owner_id=request.authuser.user_id).all()
 
         c.participate_in_pull_requests = []
         c.participate_in_pull_requests_todo = []
         done_status = set([db.ChangesetStatus.STATUS_APPROVED, db.ChangesetStatus.STATUS_REJECTED])
         for pr in db.PullRequest.query(
             include_closed=c.closed,
             reviewer_id=request.authuser.user_id,
             sorted=True,
         ):
             status = pr.user_review_status(request.authuser.user_id) # very inefficient!!!
             if status in done_status:
                 c.participate_in_pull_requests.append(pr)
             else:
                 c.participate_in_pull_requests_todo.append(pr)
 
         return base.render('/pullrequests/pullrequest_show_my.html')
 
     @LoginRequired()
     @HasRepoPermissionLevelDecorator('read')
     def index(self):
         org_repo = c.db_repo
         org_scm_instance = org_repo.scm_instance
         try:
             org_scm_instance.get_changeset()
         except EmptyRepositoryError as e:
             webutils.flash(_('There are no changesets yet'),
                     category='warning')
             raise HTTPFound(location=url('summary_home', repo_name=org_repo.repo_name))
 
         org_rev = request.GET.get('rev_end')
         # rev_start is not directly useful - its parent could however be used
         # as default for other and thus give a simple compare view
         rev_start = request.GET.get('rev_start')
         other_rev = None
         if rev_start:
             starters = org_repo.get_changeset(rev_start).parents
             if starters:
                 other_rev = starters[0].raw_id
             else:
                 other_rev = org_repo.scm_instance.EMPTY_CHANGESET
         branch = request.GET.get('branch')
 
         c.cs_repos = [(org_repo.repo_name, org_repo.repo_name)]
         c.default_cs_repo = org_repo.repo_name
         c.cs_refs, c.default_cs_ref = self._get_repo_refs(org_scm_instance, rev=org_rev, branch=branch)
 
         default_cs_ref_type, default_cs_branch, default_cs_rev = c.default_cs_ref.split(':')
         if default_cs_ref_type != 'branch':
             default_cs_branch = org_repo.get_changeset(default_cs_rev).branch
 
         # add org repo to other so we can open pull request against peer branches on itself
         c.a_repos = [(org_repo.repo_name, '%s (self)' % org_repo.repo_name)]
 
         if org_repo.parent:
             # add parent of this fork also and select it.
             # use the same branch on destination as on source, if available.
             c.a_repos.append((org_repo.parent.repo_name, '%s (parent)' % org_repo.parent.repo_name))
             c.a_repo = org_repo.parent
             c.a_refs, c.default_a_ref = self._get_repo_refs(
                     org_repo.parent.scm_instance, branch=default_cs_branch, rev=other_rev)
 
         else:
             c.a_repo = org_repo
             c.a_refs, c.default_a_ref = self._get_repo_refs(org_scm_instance, rev=other_rev)
 
         # gather forks and add to this list ... even though it is rare to
         # request forks to pull from their parent
         for fork in org_repo.forks:
             c.a_repos.append((fork.repo_name, fork.repo_name))
 
         return base.render('/pullrequests/pullrequest.html')
 
     @LoginRequired()
     @HasRepoPermissionLevelDecorator('read')
     @base.jsonify
     def repo_info(self, repo_name):
         repo = c.db_repo
         refs, selected_ref = self._get_repo_refs(repo.scm_instance)
         return {
             'description': repo.description.split('\n', 1)[0],
             'selected_ref': selected_ref,
             'refs': refs,
             }
 
     @LoginRequired()
     @HasRepoPermissionLevelDecorator('read')
     def create(self, repo_name):
         repo = c.db_repo
         try:
             _form = PullRequestForm(repo.repo_id)().to_python(request.POST)
         except formencode.Invalid as errors:
             log.error(traceback.format_exc())
             log.error(str(errors))
             msg = _('Error creating pull request: %s') % errors.msg
             webutils.flash(msg, 'error')
             raise HTTPBadRequest
 
         # heads up: org and other might seem backward here ...
         org_ref = _form['org_ref'] # will have merge_rev as rev but symbolic name
         org_repo = db.Repository.guess_instance(_form['org_repo'])
 
         other_ref = _form['other_ref'] # will have symbolic name and head revision
         other_repo = db.Repository.guess_instance(_form['other_repo'])
 
         reviewers = []
 
         title = _form['pullrequest_title']
         description = _form['pullrequest_desc'].strip()
         owner = db.User.get(request.authuser.user_id)
 
         try:
             cmd = CreatePullRequestAction(org_repo, other_repo, org_ref, other_ref, title, description, owner, reviewers)
         except CreatePullRequestAction.ValidationError as e:
             webutils.flash(e, category='error', logf=log.error)
             raise HTTPNotFound
 
         try:
             pull_request = cmd.execute()
             meta.Session().commit()
         except Exception:
             webutils.flash(_('Error occurred while creating pull request'),
                     category='error')
             log.error(traceback.format_exc())
             raise HTTPFound(location=url('pullrequest_home', repo_name=repo_name))
 
         webutils.flash(_('Successfully opened new pull request'),
                 category='success')
         raise HTTPFound(location=pull_request.url())
 
     def create_new_iteration(self, old_pull_request, new_rev, title, description, reviewers):
         owner = db.User.get(request.authuser.user_id)
         new_org_rev = self._get_ref_rev(old_pull_request.org_repo, 'rev', new_rev)
         new_other_rev = self._get_ref_rev(old_pull_request.other_repo, old_pull_request.other_ref_parts[0], old_pull_request.other_ref_parts[1])
         try:
             cmd = CreatePullRequestIterationAction(old_pull_request, new_org_rev, new_other_rev, title, description, owner, reviewers)
         except CreatePullRequestAction.ValidationError as e:
             webutils.flash(e, category='error', logf=log.error)
             raise HTTPNotFound
 
         try:
             pull_request = cmd.execute()
             meta.Session().commit()
         except Exception:
             webutils.flash(_('Error occurred while creating pull request'),
                     category='error')
             log.error(traceback.format_exc())
             raise HTTPFound(location=old_pull_request.url())
 
         webutils.flash(_('New pull request iteration created'),
                 category='success')
         raise HTTPFound(location=pull_request.url())
 
     # pullrequest_post for PR editing
     @LoginRequired()
     @HasRepoPermissionLevelDecorator('read')
     def post(self, repo_name, pull_request_id):
         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)