Introduction to Git Hooks: How to Automate Your Workflow

One of the many features of Git is its ability to run scripts or programs at various points in the Git workflow. These scripts are known as Git hooks, and they can be used to automate tasks, enforce code quality, or facilitate collaboration among team members.

In this blog post, we will introduce the concept of Git hooks, explain how they work, and provide some examples of how to use them effectively.

What are Git Hooks?

Git hooks are scripts that Git can execute before or after certain Git events. For example, Git hooks can be run before a commit is made, after a commit is made, before code is pushed to a remote repository, or after code is pulled from a remote repository.

Git hooks can be written in any scripting language that is installed on your system, such as Bash, Python, Ruby, or JavaScript. Git hooks are typically stored in a .git/hooks directory inside your Git repository, and they are named after the Git event they are associated with.

The following Git hooks are available out-of-the-box with Git

Git provides several built-in hooks that allow you to automate tasks and enforce policies at various stages of your development workflow. Here’s a brief overview of the available hooks and their typical uses:

• pre-commit: This hook runs before a commit is created. It enables you to perform checks or validations on the code being committed. For instance, you could use this hook to check for syntax errors, run tests, or enforce coding standards.

• post-commit: This hook runs after a commit is made. It can be used for actions such as sending notifications or triggering builds, ensuring that subsequent processes are initiated once the commit is complete.

• pre-push: This hook runs before code is pushed to a remote repository. It allows you to perform checks or validations on the code being pushed, such as verifying conflicts with other branches or running additional tests to ensure the integrity of the code.

• post-push: This hook runs after code is pushed to a remote repository. It can be used to carry out additional actions like updating a deployment or triggering a CI/CD pipeline, facilitating the continuation of automated processes after the push.

How do Git Hooks work?

To create a Git hook, you simply need to create a script file in the .git/hooks directory with the appropriate name for the Git event you want to associate it with. For example, if you want to create a pre-commit hook, you would create a script file named “pre-commit” in the .git/hooks directory.

Git hooks are executed with the same permissions as the user who is running the Git command. This means that Git hooks can access and modify the files in your Git repository, as well as execute any other programs that are installed on your system.

Example: Creating a pre-commit Git Hook

Let’s create a simple pre-commit Git hook that checks for trailing whitespace in our code. Trailing whitespace can be a common source of coding errors, and it is often considered bad practice in programming.

Here is the code for our pre-commit Git hook:

#!/bin/bash
# Check for trailing whitespace
if git diff --cached --check --exit-code >/dev/null ; then
    exit 0 #success exit code
else
    echo "Error: Found trailing whitespace. Please remove and try again."
    exit 1 # failure exit code
fi

This script uses the "git diff" command to check for any whitespace errors in the code that is about to be committed. If any whitespace errors are found, the script will print an error message and exit with a non-zero status code, which will prevent the commit from being made.

To use this pre-commit Git hook in our Git repository, we simply need to save the above code as a file named “pre-commit” in the .git/hooks directory of our Git repository. We also need to make sure that the file has executable permissions, which can be done with the following command:

chmod +x .git/hooks/pre-commit

Now, whenever we make a commit in our Git repository, this pre-commit Git hook will be executed automatically, and it will check for trailing whitespace in our code before allowing the commit to be made.