git-split-commit

#!/bin/bash
#
# Split the last commit into multiple patches. Usually used during
# re-basing.
#
#

usage() {
    cat <<- EOF
	Usage: $(basename $0) [--before|--after]
	    --before ... re-commit the patch before any leftovers (default)
	    --after  ... commit everything else first, then the leftover
	EOF
}

mode="before"
case "$1" in
    --after)
        mode="after"
        ;;
    --before)
        mode="before"
        ;;
    --help)
        usage
        exit 0
        ;;
    "")
        ;;
    *)
        echo "Invalid argument: $1"
        usage
        exit 1
        ;;
esac

git diff > /dev/null
if [ $? -ne 0 ]; then
    echo "Unstaged changes, please commit them first"
    exit 1
fi

readonly sha=$(git rev-list -n 1 HEAD)

git reset HEAD~1
if [ $mode = "before" ]; then
    git add -p

    if [ $? -ne 0 ]; then
        echo "---------------------------------------------"
        echo "git add -p failed, dropping you into a shell."
        echo "Exiting the shell will commit"
        $SHELL
    fi

    echo -n "Need to add any files? [y/N] "
    read addfiles

    if [ "$addfiles" = "y" -o "$addfiles" = "Y" ]; then
        echo "------------------------------"
        echo "Dropping you into a shell now."
        echo "Exiting the shell will commit."
        $SHELL
    fi

    git commit -c $sha

    echo "--------------------------------------"
    echo "Add remaining hunks now. To abort, run"
    echo "    git reset --hard $sha"

else # mode == after
    echo "---------------------------------------------------"
    echo "Starting a shell. Commit everything unrelated first"
    echo "Exiting the shell will re-commit"
    $SHELL
    git commit -ac $sha

    echo -n "Happy with the split? N will reset [Y/n] "
    read happy
    if [ "$happy" = "n" -o "$happy" = "N" ]; then
        git reset --hard $sha
    fi
fi