Git Hooks

Executables in .git/hooks/ (or core.hooksPath) named for the event. Non-zero exit aborts (except post-*). Any language; must be +x, no extension.

Distribution

.git/hooks/* is not cloned. Use a tracked dir:

git config core.hooksPath .githooks
git commit --no-verify          # bypass pre-commit + commit-msg
git push --no-verify            # bypass pre-push

Client-Side

Commit flow: pre-commit → prepare-commit-msg → editor → commit-msg → post-commit.

Hook	Args	Abort?	Use
`pre-commit`	—	yes	lint, format, fast tests
`prepare-commit-msg`	msg-file, source, sha	yes	inject ticket ID, templates
`commit-msg`	msg-file	yes	validate message format
`post-commit`	—	no	notifications
`pre-rebase`	upstream [branch]	yes	block rebasing published commits
`post-rewrite`	`amend`\|`rebase`; stdin: old→new sha	no	re-run artifact gen after amend
`post-checkout`	prev, new, branch-flag	no	LFS smudge, regenerate artifacts
`post-merge`	squash-flag	no	restore untracked state
`pre-push`	remote, url; stdin: `local-ref local-sha remote-ref remote-sha`	yes	full tests, block force-push to main
`pre-auto-gc`	—	yes	defer gc when busy

Patch flow (git am): applypatch-msg → pre-applypatch → post-applypatch.

Server-Side (on bare repo)

Hook	Args	Scope	Abort?
`pre-receive`	stdin `old new ref` per updated ref	once per push	yes (rejects all)
`update`	ref, old, new	per ref	yes (that ref only)
`post-receive`	stdin like pre-receive	once	no — CI triggers

update is the granular gatekeeper: protect branches, reject non-FF on main, require signed commits.

Debugging

GIT_TRACE=1 git commit
bash -x .git/hooks/pre-commit

Hooks reading stdin (pre-push, pre-receive) must consume it — forgetting silently deadlocks on large pushes.

Pitfalls