portupgrade "---> Backing up the old version"

[E. J. Cerejo]

kris at obsecurity.org wrote:
> On Tue, Apr 15, 2003 at 02:58:20AM -0400, E. J. Cerejo wrote:
> 
>>While using portupgrade I noticed before it deinstalls the old port it 
>>says something like "--->  Backing up the old version" and then it goes 
>>on deinstalling and installing the new version.  Where does this backup 
>>go?  I looked at the man page and it says something like /var/tmp but I 
>>went into that directory and there is nothing in there relating to a 
>>port back!  Does portupgrade delete that backup after the successful 
>>install of the new version?
> 
> 
> Yes.
> 
> Kris

I'm running out of space in /var, how do you specify an alternate path 
for that backup?