prepare-commit-msg.sh

#!/bin/bash
 
# This way you can customize which branches should be skipped when
# prepending commit message. 
if [ -z "$BRANCHES_TO_SKIP" ]; then
  BRANCHES_TO_SKIP=(master develop test)
fi
 
BRANCH_NAME=$(git symbolic-ref --short HEAD)
BRANCH_NAME="${BRANCH_NAME##*/}" #Remove feature/, hotfix/, etc.
TICKET="$(echo $BRANCH_NAME | sed -e 's/^\([A-Z]\{1,10\}-[0-9]\{1,10\}\)-.*/\1/')"
 
IS_BRANCH_EXCLUDED=$(printf "%s\n" "${BRANCHES_TO_SKIP[@]}" | grep -c "^$BRANCH_NAME$")
IS_TICKET_ALREADY_IN_COMMIT=$(grep -c "\[$TICKET\]" $1)
 
if [ -n "$TICKET" ] && ! [[ $IS_BRANCH_EXCLUDED -eq 1 ]] && ! [[ $IS_TICKET_ALREADY_IN_COMMIT -ge 1 ]]; then 
  sed -i.bak -e "1s/^/[$TICKET] /" $1
fi

Extracted ticket number if branch name also contains a descriptive name.