Show *hypo*thetical filesystem changes by a command ;) before running it on a live system

hypo.sh

#!/usr/bin/env sh
#
# Script by: github.com/nikp123
#
# Distributed under the terms of the MIT license
#
# The command requires ROOT despite the usage of fuse-overlayfs
# I look forward to fixing this in the future.
# You NEED the following commands already installed on your system:
# https://github.com/kmxz/overlayfs-tools/tree/master
# https://github.com/containers/fuse-overlayfs
#

if [ $# -lt 2 ]; then
    echo "Usage: $0 directory_to_sandbox command"
    exit -1
fi

source_dir="$1"

mkdir "$source_dir.up" "$source_dir.work"
fuse-overlayfs -o lowerdir="$source_dir",upperdir="$source_dir.up",workdir="$source_dir.work" "$source_dir"

${@:2}

echo -n "Waiting for unmount"
while ! umount "$source_dir" &> /dev/null; do
    echo -n "."
    sleep .1
done
echo ""

overlay diff -l "$source_dir" -u "$source_dir.up"

# Prompt the user with a yes/no question
echo -n "Apply changes? (y/N): "
read answer

# Check the user's response
case "$answer" in
    [yY]|[yY][eE][sS])   # If answer is yes or y (case insensitive)
        echo "Meging changes..."
        overlay merge -l "$source_dir" -u "$source_dir.up"
	./overlay-tools-*
	rm overlay-tools-*
        ;;
    *)
    	# NOOP
        ;;
esac

rm -rf "$source_dir.up" "$source_dir.work"