fix: publish keeps a closing trailer block of --message last, so git reads Co-Authored-By again (#149)

Files changed:
- CHANGES.md
- VERSION
- tools/CONTRACT.md
- tools/chemenu/commands/git_publish.py
- tools/chemenu/tests/test_git_publish.py

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SnAJ7Z3CpVD3PRbN73QtU2

tools/chemenu/tests/test_git_publish.py

@@ -969,11 +969,11 @@ def test_publish_reactive_retry_survives_a_genuine_race(repo, monkeypatch):
     raced = {"done": False}
     real_run = git_publish._run
 
-    def racy_run(args):
+    def racy_run(args, **kwargs):
         if args[:2] == ["git", "push"] and not raced["done"]:
             raced["done"] = True
             _push_from_writer(writer, "mid-race.md", "landed during the push\n")
-        return real_run(args)
+        return real_run(args, **kwargs)
 
     monkeypatch.setattr(git_publish, "_run", racy_run)
 
@@ -1391,3 +1391,98 @@ def test_gate_has_no_flag_that_opens_it(repo):
 
     params = inspect.signature(publish_command).parameters
     assert not any("remote" in name and "confirm" in name for name in params)
+
+
+# --- The commit message: "Files changed:" stays in front of a closing trailer block ---
+
+ATTRIBUTION = "Co-Authored-By: A <a@x>\nClaude-Session: https://claude.ai/code/session_x"
+
+
+def _plain(message, files):
+    """The message `publish` has always written - the layout every message without a trailer
+    block must keep, byte for byte."""
+    return message + "\n\nFiles changed:\n" + "\n".join(f"- {f}" for f in files)
+
+
+def _git_trailers(root, message):
+    return subprocess.run(
+        ["git", "interpret-trailers", "--parse", "--no-divider"],
+        cwd=root, input=message, capture_output=True, text=True, check=True,
+    ).stdout
+
+
+@pytest.mark.parametrize("message", [
+    "fix: something",
+    "fix: something\n\nA body paragraph.",
+    # A colon in prose is not a trailer: git needs every line of the last paragraph to be one
+    # (or a quarter of them, alongside a git-generated one).
+    "fix: something\n\nSee: this free paragraph has a colon in it\nand carries on in prose.",
+    # The first paragraph is the title and is never a trailer block, whatever it looks like.
+    "Co-Authored-By: A <a@x>",
+    # Trailers that are not in the last paragraph are not trailers for git either.
+    "fix: something\n\n" + ATTRIBUTION + "\n\nA closing remark.",
+])
+def test_a_message_without_a_trailer_block_is_byte_identical_to_before(repo, message):
+    assert _git_trailers(repo, message) == ""
+    assert git_publish.commit_message(message, ["kb/a.md", "kb/b.md"]) == _plain(message, ["kb/a.md", "kb/b.md"])
+
+
+def test_the_file_list_goes_in_front_of_a_closing_trailer_block(repo):
+    message = "fix: something\n\nA body.\n\n" + ATTRIBUTION
+    assert git_publish.commit_message(message, ["kb/a.md", "kb/b.md"]) == (
+        "fix: something\n\nA body.\n\nFiles changed:\n- kb/a.md\n- kb/b.md\n\n" + ATTRIBUTION
+    )
+
+
+@pytest.mark.parametrize("message", [
+    "fix: something\n\n" + ATTRIBUTION,
+    # A continuation line belongs to the trailer above it.
+    "fix: something\n\nA body.\n\nCo-Authored-By: A\n  <a@x>\nClaude-Session: x",
+    # A git-generated trailer lets a block carry non-trailer lines (the 25% rule).
+    "fix: something\n\nA body.\n\nfree text\n(cherry picked from commit abc123)\nSigned-off-by: A <a@x>",
+    # `git log` reads past a `---` line, and so does the check.
+    "fix: something\n\nA body.\n---\nmore body\n\n" + ATTRIBUTION,
+    # Trailing whitespace after the block, which `git commit` strips anyway.
+    "fix: something\n\nA body.\n\n" + ATTRIBUTION + "\n\n  \n",
+])
+def test_git_reads_the_same_trailers_after_the_file_list_is_added(repo, message):
+    """Whatever git reads as the message's trailers, it still reads from the commit message -
+    and the file list is in there in full."""
+    expected = _git_trailers(repo, message)
+    assert expected
+    result = git_publish.commit_message(message, ["kb/a.md", "kb/b.md"])
+    assert _git_trailers(repo, result) == expected
+    assert "\n\nFiles changed:\n- kb/a.md\n- kb/b.md\n\n" in result
+
+
+def test_publish_commits_trailers_git_log_can_read(repo):
+    _write_files(repo, 3)
+    _publish(message="fix: something\n\nA body.\n\n" + ATTRIBUTION)
+    assert _git(
+        repo, "log", "-1", "--format=%(trailers:key=Co-Authored-By,valueonly)"
+    ).stdout.strip() == "A <a@x>"
+    body = _git(repo, "log", "-1", "--format=%B").stdout
+    assert "Files changed:\n- kb/page0.md\n- kb/page1.md\n- kb/page2.md\n" in body
+
+
+def test_publish_without_trailers_commits_the_same_message_as_before(repo):
+    _write_files(repo, 2)
+    _publish(message="fix: something\n\nA body.")
+    assert _git(repo, "log", "-1", "--format=%B").stdout.rstrip("\n") == _plain(
+        "fix: something\n\nA body.", ["kb/page0.md", "kb/page1.md"]
+    )
+
+
+def test_a_mass_update_token_does_not_depend_on_the_message(repo):
+    """The token binds the changeset, never `--message`: one issued while publishing a plain
+    message clears the same changeset carrying a trailer block, and the trailers survive."""
+    _write_files(repo, 10)
+    with pytest.raises(typer.Exit) as excinfo:
+        _publish(message="big change")
+    assert excinfo.value.exit_code == EXIT_NEEDS_CLEARANCE
+
+    _publish(message="big change\n\n" + ATTRIBUTION, confirm=_token_for(repo))
+    assert _git(repo, "status", "--porcelain", "-uall").stdout == ""
+    assert _git(
+        repo, "log", "-1", "--format=%(trailers:key=Co-Authored-By,valueonly)"
+    ).stdout.strip() == "A <a@x>"