update /usr/ports to same version as pkg upgrade?

[Ronald Klop]

Hi,

Is it possible to update the /usr/ports tree to the same version as is  
used by the default pkg repositories?
I use some ports which are not distributed as pkgs. When I 'portsnap auto'  
the ports tree gets new updates which are not in the pkgs yet and I don't  
want to rebuild those.
I'm also able to fetch the ports tree by svn if that gives more  
possibilities than portsnap for this.

So, is there a way to know from which svn revision the pkgs are build by  
the FreeBSD servers? Or something similar.

Regards,
Ronald.