Reference

Invocation

Item	Source
Hook type	Basename of argv[0] (the name Git invoked)
Arguments	sys.argv[1:], forwarded to each subhook
Stdin	Read once; replayed to every subhook
Working dir	Repository working tree (git rev-parse)
Subhooks	hooks/<type>/* that are executable files

Do not resolve the real path of the multiplexer when deciding the hook type. A symlink named pre-commit must stay pre-commit.

Supported hook names

The allowlist matches current githooks(5) names, including pre-merge-commit, pre-push, commit-msg, prepare-commit-msg, pre-receive, update, post-rewrite, and push-to-checkout.

An unknown installed name exits 1 with Unknown hook type.

Hooks that use stdin

These hooks receive a payload on stdin. The multiplexer replays it to every subhook:

Hook	Typical stdin
pre-push	Local and remote ref lines
pre-receive	Old / new oid and ref name
post-receive	Same format as pre-receive
post-rewrite	Rewritten commit pairs
reference-transaction	Reference update lines

Hooks that use arguments

Hook	Typical arguments
commit-msg	Path to the commit message file
prepare-commit-msg	Message file, source, optional SHA
pre-push	Remote name and URL
update	Ref name, old oid, new oid
post-checkout	Previous HEAD, new HEAD, flag
post-merge	Squash flag

Exit codes

Code	Meaning
0	All subhooks succeeded, or none were found
Subhook N	First failing subhook's exit code
1	Unknown hook type or no Git working tree

Hook file

The product is the single file src/multiplexer. It uses the Python standard library only. There is no package to install or import.

Copy or symlink it into .git/hooks under the hook name you want. Python 3.13 or newer must be on PATH.