Prepend git commit messages with ticket number from branch

prepare-commit-msg.sh

#!/bin/bash

# parse ticket number (if available) and prepend commit messge with it
# as we have a pound sign (#) at the start of our messages, we should probably edit the git comment character
# git config core.commentChar ';'

branchName=$(git branch --show-current)

# sed -n : quiet, s: substitute, /: delimiter
# match everything that is not a number before a number that is at least 5 digits long
# and everything after
# replace everything with capture group 1 which is our number
ticketId=$(echo "$branchName" | sed -n 's/[^0-9]*\([0-9]\{5,\}\).*/\1/p')

# we dont want to add the ticket number if it's already there (amends)
# grep -c gets the count of occurrences
isTicketIdAlreadyThere=$(grep -c "$ticketId" "$1")

# -n check if variable is not empty (null or 0 leangth)
if [[ -n $ticketId ]] && [[ $isTicketIdAlreadyThere -eq 0 ]]; then
  # -e interprets backslash escape sequences
  # $1 is our commit file. We prepend it with our ticket id
  echo -e "#$ticketId:" "$(cat "$1")" >"$1"
fi