fix: show git stderr upon error

lektor_git_timestamp.py

@@ -7,6 +7,7 @@
 import pickle
 import re
 import subprocess
+import sys
 from contextlib import suppress
 from dataclasses import dataclass
 from typing import Any
@@ -41,7 +42,12 @@
 
 def run_git(*args: str | StrPath) -> str:
     cmd = ("git", *args)
-    proc = subprocess.run(cmd, capture_output=True, text=True, check=True)
+    try:
+        proc = subprocess.run(cmd, capture_output=True, text=True, check=True)
+    except subprocess.CalledProcessError as exc:
+        if exc.stderr is not None:
+            sys.stderr.write(exc.stderr)
+        raise
     return proc.stdout
 
 

tests/test_plugin.py

@@ -3,6 +3,7 @@
 import datetime
 import os
 import re
+import subprocess
 from typing import Iterator
 from typing import Mapping
 from typing import TYPE_CHECKING
@@ -39,6 +40,13 @@ def test_run_git() -> None:
     assert output.startswith("git version")
 
 
+def test_run_git_output_stderr_on_error(capsys: pytest.CaptureFixture[str]) -> None:
+    with pytest.raises(subprocess.CalledProcessError):
+        run_git("unknown-command-xxx")
+    out, err = capsys.readouterr()
+    assert "unknown-command-xxx" in err
+
+
 class Test__fs_mtime:
     def test(self, git_repo: DummyGitRepo) -> None:
         ts = 1589238180