Git Hooks

Git Hooks

Set up and manage Git hooks for any repository.

Use when adding automated checks to git workflows — linting, testing, commit message validation.

Requirements

• Git repository (.git/ directory must exist)
• No API keys needed

Instructions

1. Verify repo root: test -d .git && echo "OK" || echo "Not a git repo". Never create hooks outside a git repo.

2. Back up existing hooks before overwriting:

   [ -f .git/hooks/pre-commit ] && cp .git/hooks/pre-commit .git/hooks/pre-commit.bak
   

3. Create the hook and make it executable:

   cat > .git/hooks/<hook-name> << 'EOF'
   #!/bin/sh
   # hook content here
   EOF
   chmod +x .git/hooks/<hook-name>
   

Common Hooks

Pre-commit: Lint Staged Files

#!/bin/sh
STAGED=$(git diff --cached --name-only --diff-filter=ACM)
# JavaScript/TypeScript
echo "$STAGED" | grep -E '\.(js|ts|jsx|tsx)$' | xargs -r npx eslint --quiet 2>/dev/null
[ $? -ne 0 ] && echo "❌ ESLint failed" && exit 1
# Python
echo "$STAGED" | grep -E '\.py$' | xargs -r python3 -m py_compile 2>&1
[ $? -ne 0 ] && echo "❌ Python syntax check failed" && exit 1
exit 0

Pre-push: Run Tests

#!/bin/sh
[ -f package.json ] && npm test
[ -f pytest.ini ] || [ -d tests/ ] && python3 -m pytest -q
exit $?

Commit-msg: Enforce Conventional Commits

#!/bin/sh
MSG=$(cat "$1")
if ! echo "$MSG" | grep -qE '^(feat|fix|docs|style|refactor|test|chore|ci|perf|build)(\(.+\))?: .+'; then
  echo "❌ Commit message must follow Conventional Commits format"
  echo "   Example: feat(auth): add login page"
  exit 1
fi

Pre-commit: Prevent Secret Leaks

#!/bin/sh
STAGED=$(git diff --cached --diff-filter=ACM -p)
if echo "$STAGED" | grep -qEi '(api[_-]?key|secret|password|token)\s*[=:]\s*["\x27][^\s]+'; then
  echo "❌ Potential secret detected in staged changes!"
  echo "   Review your changes and use environment variables instead."
  exit 1
fi

Management Commands

# List active hooks (non-sample)
ls .git/hooks/ | grep -v '\.sample$'

# Disable a hook temporarily
chmod -x .git/hooks/pre-commit

# Re-enable
chmod +x .git/hooks/pre-commit

# Remove a hook
rm .git/hooks/pre-commit

Edge Cases & Troubleshooting

• Hook not running: Check chmod +x and shebang line (#!/bin/sh or #!/bin/bash).
• Bypass when needed: git commit --no-verify skips pre-commit and commit-msg hooks.
• Team sharing: Hooks in .git/hooks/ aren't committed. Use a hooks/ directory in repo root + git config core.hooksPath hooks/ for team-wide hooks.
• Windows compatibility: Use #!/bin/sh (not bash) for cross-platform support. Avoid bash-specific syntax.
• Slow hooks: Keep pre-commit hooks under 5 seconds. Only lint staged files, not the whole project.

Security Considerations

• Add a secret-detection hook (see above) to prevent accidental credential commits.
• Never store API keys or passwords in hook scripts themselves.