prepare-commit-msg

#!/bin/sh

# Allows us to read user input below, assigns stdin to keyboard
exec < /dev/tty

# The file that contains the commit log message is passed by git to this hook as the first argument
COMMIT_MSG_FILE="$1"

# Extract paths of staged files
STAGED_FILES=$(git diff --cached --name-only)

# Extract the first level directory from all staged files
DIRS=$(echo "$STAGED_FILES" | awk -F'/' '{print $1}' | uniq)

# Count the number of unique first level directories
DIR_COUNT=$(echo "$DIRS" | wc -l)

DIRS_ONELINE=$(echo "$DIRS" | awk 1 ORS=', ' | awk '$0=gensub(/^(.*), /,"\\1","g",$0)')

# If there's more than one directory or no directory, exit with an error or without any action
if [ $DIR_COUNT -gt 1 ]; then
    echo "Error: Multiple first-level directories detected in staged files."
    echo "       Split them into multiple commits. Only one group allowed per one commit."
    echo ""

    read -p "Abort? Y/n: " yn
    if [ "${yn:0:1}" != "n" ]; then
        exit 1
    fi
elif [ -z "$DIRS" ]; then
    exit 0
fi


# Append the directory name to the beginning of the commit message
echo "[$DIRS_ONELINE] $(cat $COMMIT_MSG_FILE)" > $COMMIT_MSG_FILE