Don't rely on subject name when determinig PR for the series

The fix in series to git branch mapping 88cb274 made _guess_pr() to
work incorrectly due to a wrong assumption there.  _guess_pr() looks
up a known open PR *by subject name*, which may not necessarily be the
right PR for a given series.

Before 88cb274 the branch name was (incorrectly) based on the oldest
series id.  However currently open PRs still use the wrong branch
name.  _guess_pr() then returns a wrong cached PR/branch.  This leads
to an exception in apply_push_comment(), because it tries to verify
that PR was successfully updated, but looks at a wrong PR.

Fix this by not using lookup in local cache by name in guess_pr().

Differential Revision: D79654888

Reviewed-by: Jordan Rome <[email protected]>
Signed-off-by: Ihor Solodrai <[email protected]>

Author: theihor

kernel_patches_daemon/branch_worker.py

@@ -767,10 +767,6 @@ async def _guess_pr(
         - try to guess based on first series
         """
 
-        # try to find amond known relevant PRs
-        if series.subject in self.prs:
-            return self.prs[series.subject]
-
         if not branch:
             # resolve branch: series -> subject -> branch
             subject = Subject(series.subject, self.patchwork)

tests/test_branch_worker.py

@@ -633,16 +633,6 @@ def test_delete_branches(self) -> None:
             ggr.assert_called_once_with(f"heads/{branch_deleted}")
             ggr.return_value.delete.assert_called_once()
 
-    @aioresponses()
-    async def test_guess_pr_return_from_active_pr_cache(self, m: aioresponses) -> None:
-        # Whatever is in our self.prs's cache dictionary will be returned.
-        series = Series(self._pw, SERIES_DATA)
-        sentinel = random.random()
-        # pyre-fixme[6]: For 2nd argument expected `PullRequest` but got `float`.
-        self._bw.prs["foo"] = sentinel
-        pr = await self._bw._guess_pr(series)
-        self.assertEqual(sentinel, pr)
-
     async def test_guess_pr_return_from_secondary_cache_with_specified_branch(
         self,
     ) -> None: