Git Hooks

What are Git Hooks?

Git hooks are scripts that run automatically when certain Git events happen, like making a commit or pushing code.

Why Use Hooks?

Hooks help you automate repetitive tasks, enforce coding standards, and catch problems early.

For example, you can:

• Run tests before every commit or push
• Check code style automatically
• Block bad commit messages
• Enforce rules for everyone on your team

Where Do Hooks Live?

Hooks are stored in .git/hooks inside your repository.

By default, you'll see sample scripts ending with .sample.

ls .git/hooks

How to Enable a Hook

To enable a hook, remove the .sample extension and make the script executable.

For example, to enable pre-commit:

mv .git/hooks/pre-commit.sample .git/hooks/pre-commit
chmod +x .git/hooks/pre-commit

On Windows, just rename the file to pre-commit and make sure it can be run by your shell (e.g. use .bat or .ps1 if needed).

Types of Hooks

There are many types of hooks, but the most common are:

• pre-commit
• commit-msg
• pre-push
• pre-receive
• post-receive

pre-commit Hook

The pre-commit hook runs before you make a commit.

You can use it to check code style, run tests, or stop a commit if something is wrong.

#!/bin/sh
# Stop commit if any .js file has "console.log"
grep -r 'console.log' *.js && {
  echo "Remove console.log before committing!"
  exit 1
}

commit-msg Hook

The commit-msg hook checks or edits the commit message.

For example, it can block commits without a ticket number.

#!/bin/sh
# Block commit if message does not contain a ticket number
if ! grep -qE 'JIRA-[0-9]+' "$1"; then
  echo "Commit message must have a ticket number (e.g. JIRA-123)"
  exit 1
fi

pre-push Hook

The pre-push hook runs before you push code to a remote.

You can use it to run tests or checks before sharing code.

#!/bin/sh
npm test || exit 1

Server-side Hooks

Some hooks (like pre-receive) run on the Git server, not your computer.

These can enforce rules for everyone who pushes to the repository.

#!/bin/sh
# Block pushes to main branch
grep refs/heads/main || exit 1

Custom Hooks

You can write any custom script as a hook.

Just put it in .git/hooks and make it executable.

#!/bin/sh
echo "Hello from my custom hook!"

Debugging and Best Practices

• Make sure your hook script is executable (chmod +x scriptname).
• Add echo statements to see what your script is doing.
• Check the exit code: exit 0 means success, exit 1 means fail.
• On Windows, use .bat or .ps1 scripts if needed.
• Keep hooks simple and fast—slow hooks slow down your workflow.
• Share useful hooks with your team (but remember: hooks are not versioned by default).