fix: reconcile ambiguous merge outcomes (#277)

src/gitea_proxy.py

@@ -1470,6 +1470,21 @@ async def pull_completion_review(repository: str, number: int) -> dict:
     }
 
 
+async def is_pull_merged_at_head(
+    repository: str, number: int, expected_head_sha: str
+) -> bool:
+    pull = await fetch(f"repos/{repository}/pulls/{number}")
+    if not isinstance(pull, dict):
+        return False
+    head_value = pull.get("head")
+    head = head_value if isinstance(head_value, dict) else {}
+    return (
+        pull.get("merged") is True
+        and pull.get("state") == "closed"
+        and head.get("sha") == expected_head_sha
+    )
+
+
 async def merge_assigned_pull(
     repository: str, number: int, expected_head_sha: str
 ) -> dict:

src/main.py

@@ -2068,9 +2068,26 @@ async def merge_assigned_pull(
             status_code=409,
         )
     except Exception:
+        try:
+            merged = await asyncio.wait_for(
+                gitea_proxy.is_pull_merged_at_head(
+                    repository, number, submission.expected_head_sha
+                ),
+                timeout=ISSUE_ACTION_TIMEOUT_SECONDS,
+            )
+        except Exception:
+            merged = False
+        if merged:
+            return {"number": number, "merged": True, "state": "closed"}
         return JSONResponse(
-            {"error": "The pull request could not be merged. It remains in My Work; please retry."},
-            status_code=503,
+            {
+                "number": number,
+                "merged": False,
+                "state": "unknown",
+                "confirmation_pending": True,
+                "error": "Merge confirmation is pending. Check its status before retrying.",
+            },
+            status_code=202,
             headers={"Retry-After": "1"},
         )