Tools/git-hooks/commit-msg

#!/bin/sh
# Commit message git hook for the SWIG repository, checking the commit message rules in CONTRIBUTING.md
# Use all the hooks in this directory by running: git config core.hooksPath Tools/git-hooks

msg_file=$1

# Drop git's comment lines (but not a line starting with an issue number such as #3554) and everything below the
# scissors line added by 'git commit --verbose'
msg=$(sed -e '/^# -* >8 -*$/,$d' -e '/^#[0-9]/!{/^#/d;}' "$msg_file")

errors=0

ai_tools='anthropic|claude[ -]?(code|opus|sonnet|haiku|fable)|copilot|cursor|codex|openai|chatgpt|gemini|aider|deepseek'
ai_tools="$ai_tools|opencode|ampcode|windsurf|codeium"
ai_coauthor=$(printf '%s\n' "$msg" | grep -n -i -E "^[[:space:]]*co-authored-by:.*($ai_tools)")
if [ -n "$ai_coauthor" ]; then
  printf 'Error: an AI tool is not a co-author, remove this Co-authored-by line:\n%s\n' "$ai_coauthor" >&2
  printf 'Disclose AI assistance with an Assisted-by trailer instead, such as: Assisted-by: Claude Code (Opus 4.8)\n' >&2
  errors=1
fi

backticks=$(printf '%s\n' "$msg" | grep -n '`')
if [ -n "$backticks" ]; then
  printf "Error: do not use backticks in a commit message, quote code with ' or \" instead:\n%s\n" "$backticks" >&2
  errors=1
fi

bad_assisted_by=$(printf '%s\n' "$msg" | grep -i '^[[:space:]]*assisted-by:' | grep -v -E '^Assisted-by: [^][()<>]+ \([^][()<>]+\)$')
context_assisted_by=$(printf '%s\n' "$msg" | grep -i '^[[:space:]]*assisted-by:.*context')
if [ -n "$bad_assisted_by$context_assisted_by" ]; then
  printf 'Error: write the Assisted-by trailer as "Assisted-by: Tool (Model)" without an email or context size, such as:\n' >&2
  printf 'Assisted-by: Claude Code (Opus 4.8)\n' >&2
  printf '%s\n' "$bad_assisted_by" "$context_assisted_by" | grep -v '^$' | sort -u >&2
  errors=1
fi

if [ $errors -ne 0 ]; then
  printf 'The commit message is saved in %s\n' "$msg_file" >&2
  exit 1
fi

# A reminder only, as whether AI tools were used cannot be checked
if ! printf '%s\n' "$msg" | grep -q '^Assisted-by:' && [ -n "$(git diff --cached --name-only -- Source Lib)" ]; then
  printf 'Note: if AI tools helped with this change to Source or Lib, add an Assisted-by trailer, see CONTRIBUTING.md\n' >&2
fi

exit 0