fixed with codex

tests/test_diff.py

@@ -0,0 +1,57 @@
+from __future__ import annotations
+
+from typing import Any
+from unittest.mock import patch
+
+import subprocess
+
+from ai_reviewer.diff import run_git_diff
+
+
+def _completed(cmd: list[str], returncode: int, stdout: str = "", stderr: str = "") -> subprocess.CompletedProcess[Any]:
+    return subprocess.CompletedProcess(cmd, returncode, stdout, stderr)
+
+
+def test_run_git_diff_prefers_direct_refs():
+    calls: list[list[str]] = []
+
+    def fake_run(cmd, check=False, capture_output=False, text=False):  # type: ignore[override]
+        calls.append(cmd)
+        if cmd[3] == "diff":
+            if cmd[4] == "base...head":
+                return _completed(cmd, 0, stdout="ok")
+            return _completed(cmd, 128, stderr="fatal")
+        raise AssertionError("fetch should not run when refs exist locally")
+
+    with patch("ai_reviewer.diff.subprocess.run", side_effect=fake_run):
+        output = run_git_diff(".", "base", "head")
+
+    assert output == "ok"
+    # Only one diff attempt should be needed when local refs exist.
+    assert len(calls) == 1
+
+
+def test_run_git_diff_falls_back_to_origin_refs_after_fetch():
+    fetched = False
+    diff_attempts: list[str] = []
+
+    def fake_run(cmd, check=False, capture_output=False, text=False):  # type: ignore[override]
+        nonlocal fetched
+        if cmd[3] == "diff":
+            diff_attempts.append(cmd[4])
+            spec = cmd[4]
+            if spec == "origin/base...origin/head" and fetched:
+                return _completed(cmd, 0, stdout="remote-ok")
+            return _completed(cmd, 128, stderr="missing ref")
+        if cmd[3] == "fetch":
+            fetched = True
+            return _completed(cmd, 0)
+        raise AssertionError("unexpected git invocation")
+
+    with patch("ai_reviewer.diff.subprocess.run", side_effect=fake_run):
+        output = run_git_diff(".", "base", "head")
+
+    assert output == "remote-ok"
+    assert "origin/base...origin/head" in diff_attempts
+    # Ensure the fallback only succeeds after fetch.
+    assert diff_attempts.index("origin/base...origin/head") > diff_attempts.index("base...head")