git commit-msg hook to put JIRA ticket ID (or other ID matching pattern) in front of the message

commit-msg

#!/bin/sh
#
# Automatically adds JIRA ticket ID based on branch name to every commit message.
#
set -x
MESSAGE=$(cat "$1")
BASEREGEX="([A-Z]{1,10}-[0-9]*)"
MSG_REGEX=$BASEREGEX

if [[ $MESSAGE =~ $MSG_REGEX ]]
then
	echo branch is already in the message
	exit
fi

BRANCH_REGEX="//?$BASEREGEX"
BRANCHNAME=$(git symbolic-ref -q HEAD)
[[ $BRANCHNAME =~ $BRANCH_REGEX ]]
TICKET="${BASH_REMATCH[1]}"

if [[ -n $TICKET ]]
then
	echo "$TICKET "$(cat "$1") > "$1"
fi