#!/bin/sh

# cpv file dest
# could extend with -r or copying multiple files

ln_or_cp () {
    f=$(df $(dirname $1) | tail -1 | awk '{ print $1 }')
    d=$(df $(dirname $2) | tail -1 | awk '{ print $1 }')
    if [ "$f" != "$d" ]; then cmd="cp -p"; else cmd="ln"; fi
    echo $cmd
}

file="$1"
dest="$2"

if [ ! -f "$file" ]; then
    echo "Error: no such file "$file". Exiting."
    exit 1
fi

# if dest is a directory, add the source file name
if [ -d "$dest" ]; then
    dest=$dest/`basename $file`
fi

# if (the new) $dest is a directory, then just bail
if [ -d "$dest" ]; then
    echo "Error: destination file ($dest) is a directory. Exiting."
    exit 1
fi

# if no such file $dest then just copy
if [ ! -f "$dest" ]; then
    $(ln_or_cp $file $dest) $file $dest
    echo "Added $(basename $dest) to $(dirname $dest)"
    exit 0
fi


# find maximum version of dest
max=0
for vf in "$dest".~[1-9]*~
do vn=`echo $vf | sed -e 's/^.*\.~\([1-9][0-9]*\)~$/\1/'`
   if [ -f $dest.~$vn~ ]; then
       if [ $max -lt $vn ]; then
	   max=$vn
       fi
   fi
done

if [ $max -eq 0 ]; then		# no current versions
    mv $dest $dest.~1~		# change version to version 1
    new=2
else
    if cmp -q $dest $dest.~$max~ >/dev/null 2>&1
    then			# they're different
	max=`expr $max + 1`	# make newer version
	mv $dest $dest.~$max~
	new=`expr $max + 1`
    else			# dest and dest.~nn~ are equal so
	rm $dest		# delete dest leave old version behind
	new=`expr $max + 1`
    fi
fi

# make new version and link it

$(ln_or_cp $file $dest.~new~) $file $dest.~$new~
echo "Added $(basename $dest.~$new~) to $(dirname $dest.~$new~)"
rm -f $dest
ln $dest.~$new~ $dest
echo "Linked $(basename $dest) to $(basename $dest.~$new~) in $(dirname $dest)"