> Error out if someone tries to mv a mount point. Old behavior was to
> move all files contained in the mounted filesystem to the dest. dir
> which could be quite nasty. Personally, I think rename(2) should
> return EPERM or EINVAL instead of EXDEV.
Obtained from: OpenBSD mv.c rev 1.6 by Todd Miller <millert@openbsd.org>
a33d9e6606