[CHG] runbot_merge: move labels cron to triggered

Missed it during the previous pass, probably because it's in the
middle of `pull_requests.py`. It's a classic template for triggered
crons since the model is just a queue of actions for the cron.

runbot_merge/data/merge_cron.xml

@@ -38,7 +38,7 @@
     <field name="state">code</field>
     <field name="code">model._send()</field>
     <field name="interval_number">10</field>
-    <field name="interval_type">minutes</field>
+    <field name="interval_type">hours</field>
     <field name="numbercall">-1</field>
     <field name="doall" eval="False"/>
     <field name="priority">70</field>

runbot_merge/models/pull_requests.py

@@ -1758,6 +1758,8 @@ class Tagging(models.Model):
             values['tags_remove'] = json.dumps(list(values['tags_remove']))
         if not isinstance(values.get('tags_add', ''), str):
             values['tags_add'] = json.dumps(list(values['tags_add']))
+        if values:
+            self.env.ref('runbot_merge.labels_cron')._trigger()
         return super().create(values)
 
     def _send(self):

runbot_merge/tests/test_by_branch.py

@@ -149,7 +149,6 @@ def test_pseudo_version_tag(env, project, make_repo, setreviewers, config):
     with repo:
         repo.post_status('staging.master', 'success', 'ci')
     env.run_crons() # should merge staging
-    env.run_crons('runbot_merge.labels_cron') # update labels
     assert pr_id.state == 'merged'
     assert pr.labels >= {'2.1'}
 
@@ -170,6 +169,5 @@ def test_pseudo_version_tag(env, project, make_repo, setreviewers, config):
     with repo:
         repo.post_status('staging.master', 'success', 'ci')
     env.run_crons() # should merge staging
-    env.run_crons('runbot_merge.labels_cron') # update labels
     assert pr_id.state == 'merged'
     assert pr.labels >= {'post-bonk'}