...

bolt_pet/updater.py

@@ -183,6 +183,22 @@ def current_ref(run: GitRunner) -> str:
     return output.strip()
 
 
+def already_at_tag(run: GitRunner, tag: str) -> bool:
+    """True if HEAD is already the commit *tag* points at.
+
+    Guards the loop you get when a release is cut without bumping
+    __version__ in the tagged commit: the checkout succeeds (it's a no-op),
+    the pet restarts, reads the same old __version__, sees the same "newer"
+    tag, and does it again — a restart every check, forever."""
+    code, head = run(["rev-parse", "HEAD"])
+    if code != 0 or not head.strip():
+        return False
+    code, target = run(["rev-parse", f"tags/{tag}^{{commit}}"])
+    if code != 0 or not target.strip():
+        return False  # tag isn't known locally yet, so we're certainly not on it
+    return head.strip() == target.strip()
+
+
 def _requirements_changed(run: GitRunner, before: str, after: str) -> bool:
     code, output = run(["diff", "--name-only", before, after, "--", "requirements.txt"])
     return code == 0 and bool(output.strip())
@@ -236,6 +252,14 @@ def apply_update(
     if code != 0:
         raise UpdateError(f"git fetch failed: {output}")
 
+    if already_at_tag(run, tag):
+        from . import __version__
+
+        raise UpdateError(
+            f"already checked out {tag}, but __version__ still reads {__version__} — "
+            f"bump it in the tagged commit, or every check re-applies the same release"
+        )
+
     code, output = run(["checkout", "--force", f"tags/{tag}"])
     if code != 0:
         raise UpdateError(f"git checkout {tag} failed: {output}")