Git Hooks Basics 🪝

Git hooks are scripts which can be executed after an action is performed, the options are: applypatch-msg, commit-msg, post-update, pre-applypatch, pre-commit, prepare-commit-msg, pre-push, pre-rebase, update.

Git hooks for a given repository are stored under .git/hooks.

[~/gitrepo]$ ls .git
branches  COMMIT_EDITMSG  config  description  FETCH_HEAD  gitweb  HEAD
hooks  index  info  logs  modules  objects  ORIG_HEAD  refs

[~/gitrepo]$ cd .git/hooks/

[~/gitrepo]$ ls -1

applypatch-msg.sample
commit-msg.sample
post-update.sample
pre-applypatch.sample
pre-commit.sample
prepare-commit-msg.sample
pre-push.sample
pre-rebase.sample
update.sample

Useful Githook Examples

Output something to /tmp/ before pushing

# create a simple pre-push githook which outputs to /tmp/githook.date.out
echo 'echo "pre-push" > /tmp/githook.`date +%s`.out' > .git/hooks/pre-push;
chmod +x ./git/hooks/pre-push

Prevent Pollution of the main Branch

Although tools like GitLab allow you to protect the main branch in a project against direct pushing, sometimes you may want to do this with bare git repositories.

This pre-commit hook helps guarantee that changes aren’t pushed to main but everything goes through a proper merging processes.

The following git hook prevents such a thing from happening.

if [ $(git symbolic-ref HEAD 2>/dev/null) == "refs/heads/main" ]
then
  echo "Cannot commit to main branch"
  exit 1
fi
exit 0

Taken from https://gist.github.com/shaneog/779e754153ee816ed226

Git Cheatsheet: Commands, Tips and Tricks 📝   Git LFS Usage on GitLab Repositories