Reference the commit explicitly (#148026)

ZainRizvi · pytorchmergebot · commit 10ffd9421607 · 2025-02-27T21:06:34.000Z
Reference the commit tested by CI explicitly, and fail the merge if the PR was updated. Tested locally Pull Request resolved: #148026 Approved by: https://github.com/seemethere, https://github.com/malfet, https://github.com/atalman
diff --git a/.github/scripts/trymerge.py b/.github/scripts/trymerge.py
@@ -1224,9 +1224,17 @@ def merge_changes(
         if not self.is_ghstack_pr():
             msg = self.gen_commit_message()
             pr_branch_name = f"__pull-request-{self.pr_num}__init__"
-            repo.fetch(f"pull/{self.pr_num}/head", pr_branch_name)
+            repo.fetch(self.last_commit()["oid"], pr_branch_name)
             repo._run_git("merge", "--squash", pr_branch_name)
             repo._run_git("commit", f'--author="{self.get_author()}"', "-m", msg)
+
+            # Did the PR change since we started the merge?
+            pulled_sha = repo.show_ref(pr_branch_name)
+            latest_pr_status = GitHubPR(self.org, self.project, self.pr_num)
+            if pulled_sha != latest_pr_status.last_commit()["oid"]:
+                raise RuntimeError(
+                    "PR has been updated since CI checks last passed. Please rerun the merge command."
+                )
             return []
         else:
             return self.merge_ghstack_into(
