Convert remaining rorepo-mutating tests to @with_rw_repo

Two further `TestRepo` tests in `test/test_repo.py` mutate
`self.rorepo` on disk:

- `test_daemon_export` toggles `self.rorepo.daemon_export`, which
  creates and removes `.git/git-daemon-export-ok` via `touch` and
  `os.unlink`.
- `test_alternates` assigns to `self.rorepo.alternates`, which
  writes and removes `<common_dir>/objects/info/alternates` via
  `open(..., "wb")` and `os.remove`.

Both bracket their writes with a save-and-restore pattern, so on
the happy path the on-disk state ends up unchanged; on a mid-test
abort the rorepo is left with stray state. Neither test produces
git lock files, which is why an earlier scope based on lock-
leaking tests did not pick them up. The contract violation is the
same in shape (transient mutation of a fixture documented as
read-only and shared across tests), and the same conversion
applies: `@with_rw_repo("HEAD")` confines the writes to a per-test
temp clone destined for cleanup.

Note that `@with_rw_repo` clones with `shared=True`, which sets
the clone's `objects/info/alternates` to point back at the source
repository's `objects/`. In `test_alternates` this means
`cur_alternates` reads back as one entry rather than the empty
list typical on the rorepo. The test's save/empty/set/restore
sequence still exercises the same setter contract; the asserts
verify what the setter wrote at each step.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: EliahKagan

test/test_repo.py

@@ -300,22 +300,24 @@ def test_init(self):
     def test_bare_property(self):
         self.rorepo.bare
 
-    def test_daemon_export(self):
-        orig_val = self.rorepo.daemon_export
-        self.rorepo.daemon_export = not orig_val
-        self.assertEqual(self.rorepo.daemon_export, (not orig_val))
-        self.rorepo.daemon_export = orig_val
-        self.assertEqual(self.rorepo.daemon_export, orig_val)
-
-    def test_alternates(self):
-        cur_alternates = self.rorepo.alternates
+    @with_rw_repo("HEAD")
+    def test_daemon_export(self, rwrepo):
+        orig_val = rwrepo.daemon_export
+        rwrepo.daemon_export = not orig_val
+        self.assertEqual(rwrepo.daemon_export, (not orig_val))
+        rwrepo.daemon_export = orig_val
+        self.assertEqual(rwrepo.daemon_export, orig_val)
+
+    @with_rw_repo("HEAD")
+    def test_alternates(self, rwrepo):
+        cur_alternates = rwrepo.alternates
         # empty alternates
-        self.rorepo.alternates = []
-        self.assertEqual(self.rorepo.alternates, [])
+        rwrepo.alternates = []
+        self.assertEqual(rwrepo.alternates, [])
         alts = ["other/location", "this/location"]
-        self.rorepo.alternates = alts
-        self.assertEqual(alts, self.rorepo.alternates)
-        self.rorepo.alternates = cur_alternates
+        rwrepo.alternates = alts
+        self.assertEqual(alts, rwrepo.alternates)
+        rwrepo.alternates = cur_alternates
 
     def test_repr(self):
         assert repr(self.rorepo).startswith("<git.repo.base.Repo ")