Unnest folders that contain only one item. Javascript version in this repo or use the shell scripts below
flatten directories with single item (move item up)
find . -type d -execdir bash -c '
for file in "$1"/*; do
[[ -f "$file" ]] && (( $((++filesCount)) > 1 )) && exit 1;
done;
((filesCount==1)) && mv -v "$file" "${file%/*}.${file##*.}"
' _ {} \; 2>/dev/null
Flatten directories containing single directory
find . -type d -execdir bash -c '
for file in "$1"/*; do
(( $((++filesCount)) > 1 )) && exit 1;
done;
((filesCount==1)) && mv "$file" "${file##*/}"
' _ {} \; 2>/dev/null
Delete empty dirs
find . -empty -type d -delete