rename-duplicate-files.sh

while IFS= read -r f; do
    file=${f##*/}
    if [ -f $dest/$file ]; then
        n=1
        while [ -f $dest/${file%%.*}-$n.${file##*.} ]
        do (( n++ ))
        done
        file=${file%%.*}-$n.${file##*.}
   fi
   mv $f $dest/$file
done