>... that the Solaris 2.5 rename [is a nop on links, but] the BSD rename
>[will handle `ln a b; mv a b' by removing `a']

The original behavior was a bug that Kirk documented.  When he was
working on the POSIX semantics description, he realized it was a bug
and fixed it.  The 1990 POSIX standard seems to require the buggy
behavior; I am not sure when/if a future POSIX will allow the correct
(i.e., BSD) behavior.

Chris