Git Hook ฝั่งไคลเอ็นต์

Welcome! In this lesson, you'll learn about Git hooks. These are scripts that Git automatically runs before or after events like committing, merging, or pushing.

Think of them as automated assistants for your Git workflow. They help enforce project standards and automate routine tasks.

Git hooks come in two flavors:

• Client-side hooks: Run on your local machine. They only affect your personal repository. Examples include `pre-commit` and `post-merge`.
• Server-side hooks: Run on the Git server. They affect all pushes to the repository. We'll cover these in a later lesson.

This lesson focuses on client-side hooks and how to use them locally.

All Git hooks are stored in the .git/hooks directory within your repository. When you initialize a new Git repository, Git populates this directory with sample hook scripts.

Let's take a look inside a typical .git/hooks folder:

By default, the sample hook scripts end with .sample, making them inactive. To activate a hook, you need to:

1. Remove the .sample extension from its filename.
2. Make the script executable.

Let's activate the pre-commit hook by renaming and making it executable:

The pre-commit hook is one of the most useful client-side hooks. It runs just before Git asks you for a commit message and before the actual commit is created.

If the script exits with a non-zero status, Git aborts the commit. This makes it perfect for:

• Running linters (e.g., ESLint, Flake8)
• Executing unit tests
• Checking for common mistakes (e.g., debug statements)

Here's a simple pre-commit script that checks if any staged files contain the word "TODO". If it finds "TODO", the commit is blocked.

You can edit the .git/hooks/pre-commit file directly to add this content:

Now, let's try to commit a file that contains "TODO". The pre-commit hook should prevent the commit.

First, create a file with "TODO", then try to commit it:

The post-merge hook runs immediately after a successful git merge or git pull (which is essentially a fetch followed by a merge or rebase).

It's useful for automating tasks that should happen after your working directory has been updated by a merge, such as:

• Installing new dependencies
• Rebuilding your project
• Updating documentation or symlinks

Imagine you're working on a project with Node.js. After merging a branch that introduced new dependencies (updated package.json), you'd want to run npm install.

Here's a post-merge script that checks if package.json was changed by the merge and runs npm install if it was:

You've learned about client-side Git hooks! Which of the following statements are TRUE about them?

Great job! You've successfully explored client-side Git hooks. Here's what we covered:

• What they are: Scripts that run automatically at specific Git events.
• Where they live: In the .git/hooks directory.
• How to activate: Rename from .sample and make executable.
• `pre-commit`: Runs before a commit, useful for validation and linting.
• `post-merge`: Runs after a merge, good for dependency updates or rebuilding.

Client-side hooks are powerful tools for personal workflow automation and local quality checks!