prepare-commit-msg git hook

prepare-commit-msg

#!/bin/bash
# Add this snippet to repo/.git/hooks/prepare-commit-msg
# 
# Credit: https://medium.com/bytelimes/automate-issue-numbers-in-git-commit-messages-2790ae6fe071
#
# Inspects branch name and checks if it contains a Jira ticket number (i.e. ABC-123).
# If yes, commit message will be automatically prepended with [ABC-123].
#
# Useful for looking through git history and relating a commit or group of commits
# back to a user story.
#

BRANCH_NAME=$(git rev-parse --abbrev-ref HEAD 2>/dev/null)

# Ensure BRANCH_NAME is not empty and is not in a detached HEAD state (i.e. rebase).
# SKIP_PREPARE_COMMIT_MSG may be used as an escape hatch to disable this hook,
# while still allowing other githooks to run.
if [ ! -z "$BRANCH_NAME" ] && [ "$BRANCH_NAME" != "HEAD" ] && [ "$SKIP_PREPARE_COMMIT_MSG" != 1 ]; then

  PREFIX_PATTERN='[A-Z]{2,5}-[0-9]{1,4}'

  [[ $BRANCH_NAME =~ $PREFIX_PATTERN ]]

  PREFIX=${BASH_REMATCH[0]}

  PREFIX_IN_COMMIT=$(grep -c "\[$PREFIX\]" $1)

  # Ensure PREFIX exists in BRANCH_NAME and is not already present in the commit message
  if [[ -n "$PREFIX" ]] && ! [[ $PREFIX_IN_COMMIT -ge 1 ]]; then
    sed -i.bak -e "1s~^~[$PREFIX] ~" $1
  fi
fi