How to automatically prepend git commit with a branch name

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=$(git symbolic-ref --short HEAD)
AFTER_FIRST_SLASH=$(echo "${BRANCH_NAME#*/}")
TICKET=$(echo "${AFTER_FIRST_SLASH%%/*}")

BRANCH_EXCLUDED=$(printf "%s\n" "${BRANCHES_TO_SKIP[@]}" | grep -c "^$TICKET$")
BRANCH_IN_COMMIT=$(grep -c "\[$TICKET\]" $1)

if [ -n "$TICKET" ] && ! [[ $BRANCH_EXCLUDED -eq 1 ]] && ! [[ $BRANCH_IN_COMMIT -ge 1 ]]; then
  sed -i.bak -e "1s/^/[$TICKET] /" $1
fi

Rename .git/hooks/prepare-commit-msg.sample to prepare-commit-msg, paste the script and make the file executable.

For instance with branch ARQ-653
$ git commit -m"Fixed bug"
will result with commit "[ARQ-653] Fixed bug"

Script handles branching name which is for example used in git-flow. Eg for branch 'feature/ABC-399' it will extract ABC-399

More elaborated way with the reasoning behind this can be found on my old and dusty blog http://blog.bartoszmajsak.com/blog/2012/11/07/lazy-developers-toolbox-number-1-prepend-git-commit-messages/

UPDATE: The script now handles multiple forward slashes in the branch name. The "ticket number" will be whatever is after the first slash in the branch, ending at the next slash or end of the string, whichever comes first.

Examples:

branch name	commit prefix
ARQ-123	[ARQ-123]
feature/ARQ-123	[ARQ-123]
feature/ARQ-123/add-login-form	[ARQ-123]