#! /bin/sh
# alt - setup alternatives symlink for file/directory $1
#       for switching between two systems.

# Assume other root mounted at /other, /etc/alternatives/$USER is
# writable.  If $1 exists, assume it belongs to OTHER system.
# If it does not exist, create a directory.

set -ex

this=$(lsb_release -sir | tr '[\n\t ]' '-')
other=$(sudo chroot /other lsb_release -sir | tr '[\n\t ]' '-')
target=$1

if test ! -e .$other$target -a ! -L .$other$target; then
    if test ! -L $target -a ! -e $target; then
	mkdir $target
    fi
    mv $target .$other$target
fi

if test -f .$other$target; then
    cp -dpv .$other$target .$this$target
elif test -d .$other$target -a ! -L .$other$target; then
    mkdir -p .$this$target
fi

alternative=$target$(pwd |tr '/' '-')
ln -s $(pwd)/.$this$target /etc/alternatives/$USER/$alternative
ln -s $(pwd)/.$other$target /other/etc/alternatives/$USER/$alternative
ln -s /etc/alternatives/$USER/$alternative $target