Git Hooks¶

Hooks are little scripts you can place in $GIT_DIR/hooks directory

prepare_commit_msg¶

This hook is invoked by git commit after preparing the default message, and before the editor is started. It takes one to three parameters.

The name of the file that contains the prepared message.
The second is message if a -m or -F option was given, template with a -t option or configuration commit.template, commit if a -c, -C or --amend option was given, merge for a merge commit or with a .git/MERGE_MSG file; and squash if a .git/SQUASH_MSG file exists.
The third is only for a commit and is the commit SHA-1.

A non-zero exit means a failure of the hook and aborts the commit.

#!/bin/sh
num_messages=5
format="# %h %s [%an]"
log="$(git log --pretty="${format}" -${num_messages})"
header="#
# last ${num_messages} messages
# ----------------------"
template() {
    echo "${header}"
    echo "${log}"
}
case "$2" in
merge|template|squash) ;;
""|commit) template >> $1;;
*)  echo "error in prepare-commit-msg hook" >&2
    exit 1
    ;;
esac