Git Hooks Example

If you are using Git as a Version Control System, then Git Hooks can surely improve your work. This repository aims to showcase what are the most useful hooks, how to use them, and what you can add to them.

1. What are Git Hooks?

Hooks are programs you can place in a hooks directory to trigger actions at certain points in git’s execution.

By default the hooks directory is .git/hooks in every local repository.

2. What Git Hooks are there?

Hook name	Description
applypatch-msg	This hook is invoked by git-am. It takes a single parameter, the name of the file that holds the proposed commit log message. Exiting with a non-zero status causes git am to abort before applying the patch.
pre-applypatch	This hook is invoked by git-am. It takes no parameter, and is invoked after the patch is applied, but before a commit is made. If it exits with non-zero status, then the working tree will not be committed after applying the patch. It can be used to inspect the current working tree and refuse to make a commit if it does not pass certain test.
post-applypatch	This hook is invoked by git-am. It takes no parameter, and is invoked after the patch is applied and a commit is made.This hook is meant primarily for notification, and cannot affect the outcome of git am
pre-commit	This hook is invoked by git-commit, and can be bypassed with the --no-verify option. It takes no parameters, and is invoked before obtaining the proposed commit log message and making a commit. Exiting with a non-zero status from this script causes the git commit command to abort before creating a commit.
pre-merge-commit	This hook is invoked by git-merge, and can be bypassed with the --no-verify option. It takes no parameters, and is invoked after the merge has been carried out successfully and before obtaining the proposed commit log message to make a commit. Exiting with a non-zero status from this script causes the git merge command to abort before creating a commit.
prepare-commit-msg	This hook is invoked by git-commit right after preparing the default log message, and before the editor is started.
commit-msg	This hook is invoked by git-commit and git-merge, and can be bypassed with the --no-verify option. It takes a single parameter, the name of the file that holds the proposed commit log message. Exiting with a non-zero status causes the command to abort.
post-commit	This hook is invoked by git-commit. It takes no parameters, and is invoked after a commit is made.
pre-rebase	This hook is called by git-rebase and can be used to prevent a branch from getting rebased. The hook may be called with one or two parameters. The first parameter is the upstream from which the series was forked. The second parameter is the branch being rebased, and is not set when rebasing the current branch.
pre-push	This hook is called by git-push and can be used to prevent a push from taking place. The hook is called with two parameters which provide the name and location of the destination remote, if a named remote is not being used both values will be the same.
pre-receive	This hook is invoked by git-receive-pack when it reacts to git push and updates reference(s) in its repository. Just before starting to update refs on the remote repository, the pre-receive hook is invoked. Its exit status determines the success or failure of the update.

3. Real world examples of hooks usage

The two most common hooks are pre-commit and pre-push. Below you can see what I am using them for:

3.1 Pre-commit

Here you can add everything you want to perform before a commit is made For example:

• Linter checks
• Reagange code
• Reformat code
• Optimze imports

#!/bin/sh

pylint

3.2 Pre-push

Here you can add what you woulf like to happen before pushing. For example:

• Make a merge or a rebase from the develop branch
• Run the tests before making a push

#!/bin/sh

git fetch
git merge origin/develop
pytest