Wrap git to add a ticket number to every commit (put this earlier in your PATH than /usr/bin/git)

git

#!/bin/bash

REAL_GIT=${REAL_GIT-/usr/bin/git}
TICKET_PREFIX=TICKET-PREFIX- # Like JIRA-, REDMINE-, CLEARQUEST- or something.
TICKET_REGEX="${TICKET_PREFIX}[0-9][0-9]*"
main() {
  local command=$1
  shift
  if [[ commit == $command ]] || [[ ticket == $command ]] ; then
    get_ticket
  fi ;
  if [[ ticket != $command ]] ; then
    $REAL_GIT $command "$@" || die "ERROR from '$REAL_GIT $command $@': $?." "$?"
  fi ;
  if [[ commit == $command ]] || [[ ticket == $command ]] ; then
    local that_commit=$($REAL_GIT log -1 --pretty=%B)
    if ! echo "$that_commit" | egrep -oh "$TICKET_REGEX" ; then
      echo "NOTE: Last commit ('$that_commit') lacks any reference to a ticket ($TICKET_PREFIX)." 1>&2
      local new_commit_msg=''
      [[ -z $that_commit ]] && new_commit_msg="$TICKET" || new_commit_msg="$that_commit $TICKET"
      $REAL_GIT commit --amend -m "$new_commit_msg"
    else
      echo "NOTE: Last commit ('$that_commit') already refers to a ticket ($TICKET_PREFIX)." 1>&2
    fi ;
  fi ;
}
die() {
  echo "${1:-ERROR}" 1>&2
  exit "${2-1}"
}
get_ticket() {
  local ticket=''
  local reporoot=$($REAL_GIT rev-parse --show-toplevel)
  local changelog=$(ls "$reporoot/" | grep CHANGELOG \
    || ls "$reporoot/" | grep -i CHANGELOG
  )
  if [[ -z $ticket ]] ; then
    if [ ${TICKET+x} ] ; then
      # Try $TICKET variable:
      ticket=$TICKET
    elif [[ $changelog ]] ; then
      # Try changelog in reverse chronological order (latest at head instead of tail):
      ticket=$(egrep "$TICKET_PREFIX" "$reporoot/$changelog" | egrep -oh "$TICKET_REGEX" | head -1)
    fi ;
  fi;
  if [[ -z $ticket ]] ; then
    # Try $DEFAULT_TICKET variable:
    if [ ${DEFAULT_TICKET+x} ] ; then
      ticket=$DEFAULT_TICKET
    fi ;
  fi;
  if ! echo "$ticket" | egrep "^$TICKET_REGEX" >/dev/null ; then
    echo "WARNING: Ticket '$ticket' does not match TICKET_REGEX /^$TICKET_REGEX/." 1>&2
  fi ;
  if [[ -z $ticket ]] ; then
    die "ERROR: Failed to determine current $TICKET_PREFIX ticket (matching /TICKET_REGEX/) via \$TICKET nor $reporoot/$changelog nor \$DEFAULT_TICKET."
    return 1
  fi ;
  TICKET=$ticket
}

main "$@"