no XLOG during COPY?

Back in February, Tom said here: 
http://archives.postgresql.org/pgsql-hackers/2008-02/msg00963.php :

> That defeats a couple of optimizations that
> Simon put in recently.  The one for no XLOG during COPY is not too
> hard to see how to re-enable, but I'm not sure what else there was.
>
>   

Could someone please point me at where this optimization was committed? 
I'm having trouble locating it.

Thanks

andrew