git commit msg hook to check that branch and commit message start with a number and that the numbers are equal

commit-msg

#!/usr/bin/env bash

current_branch="$(git rev-parse --abbrev-ref HEAD)"

branch_regex='([0-9]+)_.*'
if [[ ! $current_branch =~ $branch_regex ]]; then
    echo "branch does not start with a number" >&2
    exit 1
fi
branch_num=${BASH_REMATCH[1]}

commit_regex='#([0-9]+).*'
msg=$(head $1)
if [[ ! $msg =~ $commit_regex ]]; then
    echo $msg "commit does not start with issue number" >&2
    exit 1
fi
commit_number=${BASH_REMATCH[1]}

if [ ! "$branch_num" == "$commit_number" ]
then
  echo "branch number and commit number do not match" $branch_num $commit_number
  exit 1
fi