Hooks

Sometimes you would like Git events (commits, pushes, etc.) to trigger scripts which take care of some tasks.

Hooks are scripts that are executed before/after certain events.

They can be used to enforce nearly any kind of policy for your project.

There are client-side and server-side hooks.

Client-side hooks

You can find and edit them here:

$ ls -l .git/hooks/

• pre-commit: before commit message editor (example: make sure tests pass)
• prepare-commit-msg: before commit message editor (example: modify default messages)
• commit-msg: after commit message editor (example: validate commit message pattern)
• post-commit: after commit process (example: notification)
• pre-rebase: before rebase anything (example: disallow rebasing published commits)
• post-rewrite: run by commands that rewrite commits
• post-checkout: after successful git checkout (example: generating documentation)
• post-merge: after successful merge
• pre-push: runs during git push before any objects have been transferred
• pre-auto-gc: invoked just before the garbage collection takes place

See also pre-commit, a framework for managing and maintaining multi-language pre-commit hooks.

Example for a pre-commit hook which checks whether a Python code is PEP 8-compliant using pycodestyle:

#!/usr/bin/env bash

# ignore errors due to too long lines
pycodestyle --ignore=E501 myproject/

Server-side hooks

You can typically edit them through a web interface on GitHub/GitLab.

• pre-receive: before accepting any references
• update: like pre-receive but runs once per pushed branch

• post-receive: after entire process is completed

• Typical use:
  • Maintenance work
  • Automated tests
  • Refreshing of documentation/website
  • Sanity checks
  • Code style checks
  • Email notification
  • Rebuilding software packages