drush subversion

I love drush, but since moving to version 3 recently, I'm having problems with drush up.

I use subversion for version control, and when I try to run update, the first thing it does is to move the entire directory of any module that needs updates to the backups tree. This sounds like a good idea, but unfortunately my .svn files are moved too, giving me subversion errors, and essentially losing my historical changelog.