An audit found the guard could miss commits it exists to catch.
1. SIGPIPE. Three inner checks used `printf ... | grep -q` under
`set -euo pipefail`. When grep -q matches early it exits, printf dies of
SIGPIPE, pipefail turns the pipeline non-zero, the `if` goes false, and the
offending commit is silently not reported — the guard then prints its
success line. This file already documents the hazard in a comment and had
fixed it for the two outer pre-filters; the three inner ones were left as
pipes. Now here-strings, like the rest.
Demonstrated on a synthetic revert-style commit (an AI trailer quoted near
the top, then a 200KB body): the pipe form MISSES it, the here-string form
detects it. A trailer in the conventional last position happens to survive
the pipe form, because grep must read to the end before matching — which is
why this never showed up in practice.
2. `chatgpt` was in BAD_NAME and BAD_ANY but not BAD_TRAILER, so a
Co-authored-by naming ChatGPT with an email outside anthropic.com/openai.com
was not caught. Confirmed by test, then added.
Verified before pushing this time: the amended script flags an AI-authored
commit, a large-body early trailer, and a ChatGPT trailer, and scans
claude_guide's full 345-commit history with zero false positives — that repo
has 46 commits with Claude or Anthropic in the subject, none of which are
identity or trailer hits.
yeasy