Feature request, mv

[Joshua Hudson]

In some cases, it is desirable to rename something on top of a
symbolic link to a directory:

$ mkdir www1.0
$ (cd www1.0 && tar -zxf /tmp/www.new.tgz)
$ ln -s www1.0 www

(some time later)

$ mkdir www1.1
$ (cd www1.1 && tar -zxf /tmp/www.updated.tgz)
$ ln -s www1.0 tmp
$ mv tmp www

The desired behavour is the instantous replacement of the www dir with
no time that the site is down (mv is atomic, ln -fs is not).

However, this sequence of operations moves tmp inside www.
Perhaps an option that is "just execute the system call!" would help, along
the lines of "ln -d" and "rm -d", for which I take -d as meaning the same thing.
For sanity reasons, you might want to ensure that there is only *one* source.