Ensure the Jira slug is in the commit summary line

commit-msg

#!/usr/bin/env bash
# -*- mode: sh; -*-
#
# commit-msg
#
# Ensure that the commit message has the correct summary line with Jira slug.
#
# See also: git-hook(1), githooks(5)
#

set -euo pipefail

COMMIT_MSG_FILE="$1"
COMMIT_MSG=`head -n1 $COMMIT_MSG_FILE`
PATTERN="^([A-Z][A-Z0-9]+-[0-9]+)"

if [[ ! ${COMMIT_MSG} =~ $PATTERN ]]
then
  echo "ERROR! Commit message lacks Jira slug." >&2

  BRANCH_NAME=$(git symbolic-ref --short HEAD)
  if [[ $BRANCH_NAME =~ $PATTERN ]]
  then
    echo "Branch name matches Jira slug. Prepending to commit summary." >&2
    sed -i '' "1s/^/${BASH_REMATCH[1]} /" "$COMMIT_MSG_FILE"
  else
    echo "ERROR! Bad commit message. Add a Jira slug and retry." >&2
    exit 1
  fi
fi