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title Pre-commit Hook
description How to create a Git pre-commit hook that validates staged changes before every commit.
section playbook/pre-commit-hook
order 89

Pre-commit Hook

A pre-commit hook runs automatically before every commit. If the script exits with a non-zero code, the commit is aborted. Use it to catch problems early — linting errors, TODO markers, large files, or secrets.

Create the hook

$ cat > .git/hooks/pre-commit << 'EOF'
#!/bin/sh
# Reject commits that contain TODO
if git diff --cached --quiet -S "TODO"; then
  exit 0
fi
echo "Error: commit contains TODO"
exit 1
EOF
$ chmod +x .git/hooks/pre-commit

How it works

  1. You run git commit.
  2. Git executes .git/hooks/pre-commit before opening the message editor.
  3. If the script exits 0, the commit proceeds. Any other exit code aborts it.

Common checks

  • Lint staged files — run your linter on git diff --cached --name-only output.
  • Detect secrets — search for API keys, tokens, or passwords in the diff.
  • Enforce file size limits — reject files above a threshold.

Sharing pre-commit hooks

Hooks in .git/hooks/ are local and not committed. To share them with the team, see the Hooks recipe for the core.hooksPath approach.

Bypassing

$ git commit --no-verify -m "WIP: skip hooks"

Use sparingly — hooks exist for a reason.