git `prepare-commit-msg` - prepend branch name when branch matches `PROJECT-[0-9]+`

prepare-commit-msg

#!/bin/bash

BRANCH_NAME=$(git symbolic-ref --short HEAD)
BRANCH_NAME="${BRANCH_NAME##*/}"

BRANCH_MATCHES_PATTERN=0
if [[ $BRANCH_NAME == PROJECT-* ]]
then
  BRANCH_MATCHES_PATTERN=1
fi

PREPEND_VAL=$(echo $BRANCH_NAME | grep -Eow 'PROJECT-[0-9]+')

MSG_ALREADY_THERE=0

if [[ -z "$PREPEND_VAL" ]]
then
	# This is the case where the branch doesn't match the pattern
	MSG_ALREADY_THERE=1
else
	head -1 $1 | grep $PREPEND_VAL > /dev/null
	if [[ $? -eq 0 ]]
	then
		MSG_ALREADY_THERE=1
	fi
fi

if [ -n "$BRANCH_NAME" ] && [[ $BRANCH_MATCHES_PATTERN -eq 1 ]] && [[ $MSG_ALREADY_THERE -eq 0 ]]; then
  sed -i.bak -e "1s/^/[$PREPEND_VAL] /" $1
fi