cp: implement --update and --remove-destination?

[shen long]

How about implementing these 2 options?

--remove-destination
deletes the actual file before writing the new contents, this is useful for
gnu cp, as it follows symlinks by default...overwriting a symlink equals to
overwriting the file it points to... bad.

Although gnu cp and busybox cp behave differently from what i can tell

-u, --update
overwrites the target file only if the source is newer... i guess this
has to with
"modified time"?

Well, it makes sense when copying many files or directories