[IMP] *: note to merge using mergebot in conflict message

The message has a lot of info, but left the merging bit
unwritten. Correct this issue.

Fixes #765

forwardport/tests/test_conflicts.py

@@ -50,6 +50,7 @@ def test_conflict(env, config, make_repo, users):
     assert prc_id.state == 'opened'
 
     p = prod.commit(p_0)
+    prc = prod.get_pr(prc_id.number)
     c = prod.commit(prc_id.head)
     assert c.author == p.author
     # ignore date as we're specifically not keeping the original's
@@ -66,6 +67,33 @@ xxx
 >>>\x3e>>> [\da-f]{7,}.*
 '''),
     }
+    assert prc.comments == [
+        seen(env, prc, users),
+        (users['user'], re_matches(
+fr'''@{users['user']} @{users['reviewer']} cherrypicking of pull request {pra_id.display_name} failed\.
+
+stdout:
+```
+Auto-merging h
+CONFLICT \(add/add\): Merge conflict in h
+
+```
+
+stderr:
+```
+.*
+```
+
+Either perform the forward-port manually \(and push to this branch, proceeding as usual\) or close this PR \(maybe\?\)\.
+
+In the former case, you may want to edit this PR message as well\.
+
+:warning: after resolving this conflict, you will need to merge it via @{project.github_prefix}\.
+
+More info at https://github\.com/odoo/odoo/wiki/Mergebot#forward-port
+''', re.DOTALL))
+    ]
+
     prb = prod.get_pr(prb_id.number)
     assert prb.comments == [
         seen(env, prb, users),

mergebot_test_utils/utils.py

@@ -50,7 +50,7 @@ class re_matches:
         return self._r.match(text)
 
     def __repr__(self):
-        return self._r.pattern + '...'
+        return repr(self._r.pattern)
 
 def seen(env, pr, users):
     return users['user'], f'[Pull request status dashboard]({to_pr(env, pr).url}).'

runbot_merge/data/runbot_merge.pull_requests.feedback.template.csv

@@ -143,6 +143,8 @@ runbot_merge.forwardport.failure,"{pr.ping}cherrypicking of pull request {pr.sou
 Either perform the forward-port manually (and push to this branch, proceeding as usual) or close this PR (maybe?).
 
 In the former case, you may want to edit this PR message as well.
+
+:warning: after resolving this conflict, you will need to merge it via @{pr.repository.project_id.github_prefix}.
 {footer}","Comment when a forward-port failed.
 
 pr: the new pr (in failure)