new=/dist
old=/dist_old
diff=/dist_upgrade

cd $new
for f in *f
do
# Diff the files - ignore the output...
    diff $f $old > /dev/null 2>&1
# ...but get the status
    status=$?
    if [ $status -eq 0 ] ; then
# Files are identical - don't copy the file
        echo $f unchanged
    elif [ $status -eq 1 ] ; then
# Files differ - copy new file
        echo $f changed
        cp $f $diff
    elif [ $status -eq 2 ] ; then
# Old file doesn't exist - copy new file
        echo old $f does not exist
        cp $f $diff
    fi
done