gh-40839: Fix in label synchronization bot according to issue #40758
    
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This PR fixes #40758.

> The action
https://github.com/sagemath/sage/blob/develop/.github/sync_labels.py
should not change "needs work" (maybe "needs info" too, but we don't use
that as much so I'm not sure if it has different behaviour currently) to
"needs review" when the commit message matches the default message for a
merge commit.
Alternatives Considered

This is achieved by ignoring merge commits when the latest commit date
is determined in case a `s: needs_work` label exists. Since `s:
needs_work` persists if there is a more recent review requesting changes
this should solve the problem.

> Merging develop should still trigger a new CI run. I don't imagine
that this change would effect that though.

This remains unchanged.

> Check whether merging from the command line with git and merging from
the GitHub web interface generate the same default merge commit
messages.

In both cases, the predefined message begins with `Merge` and contains
the word `develop`. I just check that this is valid. However, note that
the user (at least in the in the command line) has the option of
changing the messages. Therefore, we generally cannot detect merge
commits exactly.

This PR also implements a new method `test_method` just for test
purposes. This allows to run arbitrary methods of the class from the
command line.


### 📝 Checklist

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- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [x] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

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URL: #40839
Reported by: Sebastian Oehms
Reviewer(s): Sebastian Oehms, Vincent Macri

Author: Release Manager

.github/sync_labels.py

@@ -408,7 +408,17 @@ def get_commits(self):
             return self._commits
 
         self._commits = self.view('commits')
-        self._commit_date = max( com['committedDate'] for com in self._commits )
+
+        # ignore merge commits with the develop branch for _commit_date unless positive review is set
+        date_commits = list(self._commits)
+        if Status.positive_review.value not in self.get_labels():
+            for com in self._commits:
+                message =  com['messageHeadline']
+                if message.startswith('Merge') and 'develop' in message:
+                    debug('Ignore merge commit %s for commit_date' % com['oid'])
+                    date_commits.remove(com)
+
+        self._commit_date = max(com['committedDate'] for com in date_commits)
         info('Commits until %s for %s: %s' % (self._commit_date, self._issue, self._commits))
         return self._commits
 
@@ -1034,6 +1044,35 @@ def run_tests(self):
             elif self.is_pull_request():
                 self.run(action)
 
+    def test_method(self, method, *args, **kwds):
+        r"""
+        Run the given method for testing.
+
+        EXAMPLES::
+
+            sage$ python .github/sync_labels.py https://github.com/sagemath/sage/pull/40634 soehms is_auth_team_member "{'login': 'soehms'}" -t
+            INFO:root:cmdline_args (4) ['https://github.com/sagemath/sage/pull/40634', 'soehms', 'is_auth_team_member', "{'login': 'soehms'}"]
+            ...
+            DEBUG:root:call is_auth_team_member with args () and kwds {'login': 'soehms'}
+            DEBUG:root:================================================================================
+            DEBUG:root:Execute command: gh api -X GET -H "Accept: application/vnd.github+json" /orgs/sagemath/teams/triage/memberships/soehms
+            INFO:root:User soehms is a member of triage
+            INFO:root:result of is_auth_team_member with args () and kwds {'login': 'soehms'} is True
+            INFO:root:================================================================================
+            ...
+        """
+        if hasattr(self, method):
+            meth = self.__getattribute__(method)
+            if callable(meth):
+                debug('call %s with args %s and kwds %s' % (method, args, kwds))
+                debug('='*80)
+                res = meth(*args, **kwds)
+                info('result of %s with args %s and kwds %s is %s' % (method, args, kwds, res))
+                info('='*80)
+                debug('state of self: %s' % self.__dict__)
+                return
+        raise ValueError('%s is not a method of %s' % (method, self))
+
 
 ###############################################################################
 # Main
@@ -1068,8 +1107,10 @@ def run_tests(self):
 num_args = len(cmdline_args)
 info('cmdline_args (%s) %s' % (num_args, cmdline_args))
 
-if run_tests and num_args in (1,2):
-    if num_args == 2:
+if run_tests:
+    if num_args == 4:
+        url, actor, method, args = cmdline_args
+    elif num_args == 2:
         url, actor = cmdline_args
     else:
         url, = cmdline_args
@@ -1079,7 +1120,10 @@ def run_tests(self):
     info('actor: %s' % actor)
 
     gh = GhLabelSynchronizer(url, actor)
-    gh.run_tests()
+    if num_args == 4:
+        gh.test_method(method, **eval(args))
+    else:
+        gh.run_tests()
 
 elif num_args == 5:
     action, url, actor, label, rev_state = cmdline_args