...

tests/test_updater.py

@@ -67,12 +67,15 @@ class FakeGit:
     *failures* maps a leading-args tuple to the (code, output) it should
     return, so a test can make exactly one command fail."""
 
-    def __init__(self, ref="main", dirty=False, failures=None, requirements_changed=False):
+    def __init__(self, ref="main", dirty=False, failures=None, requirements_changed=False,
+                 head="abc1234", tag_commit="def5678"):
         self.calls = []
         self._ref = ref
         self._dirty = dirty
         self._failures = failures or {}
         self._requirements_changed = requirements_changed
+        self._head = head
+        self._tag_commit = tag_commit  # equal to head = "already on this tag"
 
     def __call__(self, args):
         self.calls.append(list(args))
@@ -87,7 +90,7 @@ class FakeGit:
         if head == "symbolic-ref":
             return (0, self._ref) if self._ref else (1, "")
         if head == "rev-parse":
-            return 0, "abc1234"
+            return 0, self._tag_commit if args[1].startswith("tags/") else self._head
         if head == "diff":
             return 0, "requirements.txt" if self._requirements_changed else ""
         return 0, ""
@@ -160,6 +163,26 @@ def test_a_verify_that_raises_something_unexpected_still_rolls_back(tmp_path):
     assert ["checkout", "--force", "main"] in git.calls
 
 
+def test_a_release_tagged_without_bumping_the_version_does_not_loop(tmp_path):
+    """Cut a release but forget to bump __version__ in the tagged commit and
+    every check would see the same "newer" tag: check out (a no-op), restart,
+    read the old version, repeat — a restart loop every check interval."""
+    git = FakeGit(head="same1234", tag_commit="same1234")
+
+    with pytest.raises(updater.UpdateError, match="bump it in the tagged commit"):
+        updater.apply_update("v0.2.1", run=git, repo=tmp_path, install_deps=False,
+                             verify=lambda repo: None)
+
+    assert "checkout" not in git.commands()  # nothing moved, so nothing to restart into
+
+
+def test_an_unknown_tag_is_not_mistaken_for_being_already_on_it(tmp_path):
+    git = FakeGit(failures={("rev-parse", "tags/"): (128, "unknown revision")})
+    # The failure key matches by prefix, so make it explicit that a tag we
+    # can't resolve means "not there yet" rather than "already applied".
+    assert updater.already_at_tag(git, "v9.9.9") is False
+
+
 def test_a_failed_fetch_never_moves_the_checkout(tmp_path):
     git = FakeGit(failures={("fetch",): (1, "could not resolve host")})
     with pytest.raises(updater.UpdateError, match="git fetch failed"):