Git Hooks
Git Hooks are scripts that Git executes before or after events such as commit, push, and receive. These hooks are local to the repository and are not pushed or pulled with other repository contents. Here's an in-depth look at Git Hooks:
Types of Git Hooks
- Client-Side Hooks:
- pre-commit - Runs before a commit is made. It can check the commit message, coding standards, etc.
- prepare-commit-msg - Runs before the commit message editor is fired up but after the default message is created.
- commit-msg - Runs after the commit message is edited but before the commit is made.
- post-commit - Runs after the commit operation is completed.
- pre-rebase - Runs before a rebase is performed, allowing for checks or alterations.
- post-rewrite - Runs after commands like
git commit --amend or git rebase that rewrite commits.
- pre-push - Runs before pushing commits to a remote repository.
- Server-Side Hooks:
- pre-receive - Runs on the server when a push is received. It can reject pushes based on content.
- update - Similar to pre-receive but runs once for each ref being updated.
- post-receive - Runs after the entire push process is completed.
- post-update - Similar to post-receive but runs after all refs are updated.
History and Context
Git Hooks have been part of Git since its inception in 2005 by Linus Torvalds. They were introduced to provide developers with a way to customize Git's behavior. Initially, hooks were limited in functionality, but over time, as Git evolved, the capabilities and number of hooks expanded to meet the growing needs of developers for automation and enforcement of coding standards.
The concept of hooks was influenced by similar mechanisms in other version control systems like Subversion, which had pre-commit and post-commit hooks. However, Git's distributed nature meant that hooks had to be more versatile, allowing for both local and remote repository actions.
Usage and Best Practices
- Location: Hooks are stored in the
.git/hooks directory within a Git repository.
- Scripting Languages: Hooks can be written in any scripting language, though shell scripts are common due to their simplicity.
- Permissions: Hooks must be executable. On Unix-like systems, this means having the executable permission bit set.
- Sharing Hooks: While hooks are not transferred during a clone, they can be version-controlled in a separate directory or through tools like Husky.
- Security: Hooks can pose security risks if not managed properly since they execute code. It's crucial to review hooks from unknown sources before using them.
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