fix(git): omit git_reflog old_sha under all=True (interleaved refs)

src/mcp_server_git/git/_commit_ops.py

@@ -309,6 +309,11 @@ def git_reflog(
         %gP (reflog parent selector) yields a reflog selector like 'HEAD@{1}',
         not a commit SHA. old_sha is instead taken from entry[i+1].new_sha,
         which is always the commit HEAD pointed to before entry[i]'s operation.
+
+        old_sha is provided only for single-ref reflogs (all=False). Under
+        all=True, entries from different refs are interleaved so the adjacent
+        entry may belong to another ref, making derivation unreliable. old_sha
+        is therefore omitted entirely when all=True.
     """
     try:
         # %H = new (post-move) full SHA, %gD = reflog selector (HEAD@{0}),
@@ -364,8 +369,11 @@ def git_reflog(
             })
 
         # old_sha for entry[i] = entry[i+1].new_sha (reflog is newest-first).
-        for i in range(len(entries) - 1):
-            entries[i]["old_sha"] = entries[i + 1]["new_sha"]
+        # Only valid for single-ref reflogs; under all=True entries from different
+        # refs are interleaved so skip derivation entirely.
+        if not all:  # noqa: A002
+            for i in range(len(entries) - 1):
+                entries[i]["old_sha"] = entries[i + 1]["new_sha"]
 
         # Warn on large output, mirroring git_show's 50KB threshold.
         serialized_size = len(str(entries))

tests/unit/git/test_git_reflog.py

@@ -202,6 +202,29 @@ def test_git_reflog_all_false_does_not_pass_all_flag(self):
         args = mock_repo.git.reflog.call_args[0]
         assert "--all" not in args
 
+    def test_git_reflog_all_true_omits_old_sha_from_every_entry(self):
+        """Under all=True, no entry should contain old_sha (interleaved refs make
+        adjacent-entry derivation unreliable); new_sha/label/action must still be present."""
+        mock_repo = Mock()
+        sha0 = "c" * 40  # HEAD@{0} — could be from refs/heads/main
+        sha1 = "b" * 40  # HEAD@{1} — could be from refs/heads/feature (different ref)
+        sha2 = "a" * 40  # HEAD@{2}
+        mock_repo.git.reflog.return_value = _make_raw(
+            (sha0, "refs/heads/main@{0}", "commit: update main"),
+            (sha1, "refs/heads/feature@{0}", "commit: add feature"),
+            (sha2, "refs/heads/main@{1}", "commit: initial"),
+        )
+
+        result = git_reflog(mock_repo, all=True)
+
+        assert isinstance(result, list)
+        assert len(result) == 3
+        for entry in result:
+            assert "old_sha" not in entry, f"old_sha must be absent under all=True, got: {entry}"
+            assert "new_sha" in entry
+            assert "label" in entry
+            assert "action" in entry
+
 
 class TestGitReflogMultipleEntries:
     """Test parsing of multiple reflog entries."""