#!/bin/sh
ticket_number_rx='[A-Z]+\-\d{2,5}'  # if you pass ticket like prefix/GT-123-foo-bar
ticket_number=$(git symbolic-ref HEAD | grep -oE -m 1 $ticket_number_rx)
if [ -n "$ticket_number" ]; then
    if ! head -n 1 $1 | grep -qw $ticket_number; then
        ticket_template="(refs $ticket_number)"
        sed -ie "1 s/$/ $ticket_template/" $1
    fi
fi