feat(hooks): scan file-backed messages and harden rm parsing

Two audit gaps in the confirmation hooks, plus the test harness they were missing.

The git-commit and gh-pr-create hooks scanned for AI attribution but only saw inline messages. A commit made with -F/--file or a PR made with --body-file slipped through, since the hook stored a placeholder instead of the file's text, and the publish flow uses -F constantly. A new read_referenced_file helper in _common.py reads the referenced local file (missing, oversized, or non-UTF-8 returns None, which means "couldn't inspect" and never "clean"), so attribution scanning now sees the real committed and posted text. An unreadable file falls through to the existing ask-anyway path.

destructive-bash-confirm.py parsed rm flags by splitting on whitespace, which mangled quoted paths and missed flag variants. detect_rm_rf now tokenizes with shlex, so quoted or spaced paths and combined, separate, or reordered flags all parse. It fails toward asking (a sentinel that still fires the modal) on unbalanced quotes, or when a forced recursive rm sits alongside a pipeline, compound command, substitution, or redirect, since target attribution isn't trustworthy there. The supported and unsupported shell constructs are documented in the docstrings.

These hooks had no tests and weren't in make test. Added a pytest harness under hooks/tests (an importlib-by-path loader, since the hook filenames are hyphenated) with 54 tests across the three hooks and the shared helper, and wired hooks/tests into make test. Full suite green.

1 files changed, 74 insertions, 0 deletions

diff --git a/hooks/tests/test_common.py b/hooks/tests/test_common.py
new file mode 100644
index 0000000..10e6097
--- /dev/null
+++ b/hooks/tests/test_common.py
@@ -0,0 +1,74 @@
+"""Tests for hooks/_common.py — read_referenced_file and scan_attribution."""
+
+import sys
+from pathlib import Path
+
+HOOKS_DIR = Path(__file__).resolve().parent.parent
+if str(HOOKS_DIR) not in sys.path:
+    sys.path.insert(0, str(HOOKS_DIR))
+
+import _common  # noqa: E402
+
+
+# --- read_referenced_file: normal cases ------------------------------------
+
+def test_read_referenced_file_returns_content(tmp_path):
+    f = tmp_path / "msg.txt"
+    f.write_text("hello world\n")
+    assert _common.read_referenced_file(str(f)) == "hello world\n"
+
+
+def test_read_referenced_file_expands_user(tmp_path, monkeypatch):
+    # Point HOME at tmp_path so ~/msg.txt resolves under it.
+    monkeypatch.setenv("HOME", str(tmp_path))
+    monkeypatch.setattr(Path, "home", lambda: tmp_path, raising=False)
+    f = tmp_path / "msg.txt"
+    f.write_text("tilde body")
+    assert _common.read_referenced_file("~/msg.txt") == "tilde body"
+
+
+# --- read_referenced_file: error / boundary cases --------------------------
+
+def test_read_referenced_file_missing_returns_none(tmp_path):
+    assert _common.read_referenced_file(str(tmp_path / "nope.txt")) is None
+
+
+def test_read_referenced_file_directory_returns_none(tmp_path):
+    # A directory is not a regular file.
+    assert _common.read_referenced_file(str(tmp_path)) is None
+
+
+def test_read_referenced_file_oversized_returns_none(tmp_path):
+    f = tmp_path / "big.txt"
+    f.write_text("x" * 50)
+    assert _common.read_referenced_file(str(f), max_bytes=10) is None
+
+
+def test_read_referenced_file_at_limit_is_read(tmp_path):
+    f = tmp_path / "edge.txt"
+    f.write_text("12345")  # exactly 5 bytes
+    assert _common.read_referenced_file(str(f), max_bytes=5) == "12345"
+
+
+def test_read_referenced_file_invalid_utf8_returns_none(tmp_path):
+    f = tmp_path / "bin.dat"
+    f.write_bytes(b"\xff\xfe\x00bad")
+    assert _common.read_referenced_file(str(f)) is None
+
+
+def test_read_referenced_file_empty_string_path_returns_none():
+    assert _common.read_referenced_file("") is None
+
+
+# --- scan_attribution sanity (relied on by the file-backed tests) ----------
+
+def test_scan_attribution_catches_coauthor():
+    assert _common.scan_attribution("Co-Authored-By: Claude")
+
+
+def test_scan_attribution_catches_robot_emoji():
+    assert _common.scan_attribution("nice work \U0001F916")
+
+
+def test_scan_attribution_clean_text_empty():
+    assert _common.scan_attribution("fix: tidy up the parser") == []