> In a rename, where the old and the new name are links to the same
> file, netbsd deletes the old name. Linux does nothing.

> OTOH, the netbsd man page explicitly states:

>      If both from and to are pathnames of the same existing file in the file
>      system's name space, rename() returns successfully and performs no other
>      action.

For what it may be worth, I think NetBSD's behaviour is right and its
manpage needs fixing.  I believe that in general the effect of a
successful rename(src,dst) should be as if the sequence unlink(dst),
link(src,dst), unlink(src) had been done, and that this shouldn't be
affected by whether src and dst started out being hardlinks to the same
object (file or not).

Now, if both src and dst not only refer to the same object but refer to
it via the same link, which is what I suspect that paragraph was
intended to cover, _then_ rename() should do nothing.  I'm not sure how
best to phrase this.  Perhaps something like the above sequence of
unlink/link/unlink, with the additional caveat that if the unlink(dst)
would cause not only dst but also src to vanish, the rename() call
succeeds without doing anything.

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