#!/bin/sh

# cpv file dest
# could extend with -r or copying multiple files
# could change from cp to ln

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


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

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

# if no such file $dest then just copy
if [ ! -f "$dest" ]; then
    ln $file $dest		#WAS cp -p $file $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

ln $file $dest.~$new~		# cp -p $file $dest.~$new~
ln $dest.~$new~ $dest		# and link it