pre-commit hook which fails when untracked files are present in working tree

pre-commit

#!/bin/sh

untrackedFiles=$(git ls-files --others --exclude-standard)

if [ ! -z "$untrackedFiles" ]
then
    echo "There are untracked files in the working tree:"
    echo "$untrackedFiles"
    echo ""
    echo "Are you sure you aren't forgetting something?"
    echo "Aborting commit..."
    exit 1
fi