Prepend JIRA Card number in Git commit message

git-commit-message.sh

#!/bin/bash

BRANCH_NAME=$(git rev-parse --abbrev-ref HEAD 2>/dev/null)
PREFIX_PATTERN='[A-Za-z]{2,10}(-|_)[0-9]{1,6}'

# 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 ] && [[ $BRANCH_NAME =~ $PREFIX_PATTERN ]]; then

  PREFIX=${BASH_REMATCH[0]}
  PREFIX_FORMATTED=$(echo "${BASH_REMATCH[0]}" | tr '[:lower:]' '[:upper:]')
  # Grab insensitive prefix in text at the beginning, if any. Ignore first and last character.
  PREFIX_TEXT_IN_COMMIT=$(head -n 1 $1 | egrep -io -m 1 "^.?$PREFIX." | egrep -io "$PREFIX")

  # If prefix is included in commit message ensure it is uppercased
  # Enforce standard of [ABC-123] and add space if needed.
  if [ ! -z "$PREFIX_TEXT_IN_COMMIT" ]; then
    sed -i.bak "s/[^ A-Za-z0-9]*$PREFIX_TEXT_IN_COMMIT[^ A-Za-z0-9]*[ ]*/[$PREFIX_FORMATTED] /1" $1
  fi

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

fi

The $1 is the path of the .git/COMMIT_EDITMSG file in that repository.
This handles the following cases (without caring for case sensitivity in branch) and ABC-123 as well as ABC_123

BRANCH name	CommitMessage	Result
hello_there_you	Did a thing	Did a thing
ABC-123	Did a thing	[ABC-123] Did a thing
ABC-123	[ABC-123] Did a thing	[ABC-123] Did a thing
ABC-123	{ABC-123} Did a thing	[ABC-123] Did a thing
ABC-123	ABC-123: Did a thing	[ABC-123] Did a thing
ABC-123	{ABC-123:} Did a thing	[ABC-123] Did a thing
ABC-123	[ABC-123](lots of spaces) Did a thing	[ABC-123] Did a thing
ABC-123	[ABC-123] Did a thing relevant to ABC-5432	[ABC-123] Did a thing relevant to ABC-5432
ABC-123-hot-fix	Hot fix	[ABC-123] Hotfix
ABC-123-hot-fix	ABC-123: Hot fix	[ABC-123] Hotfix