rewrite question - magento in subfolder

[liamstask]

I've just started trying to get a site of mine switched over to nginx, and have enjoyed it so far but I've come up against a rewrite issue I haven't been able to solve easily.  We're running an instance of magento at the location mysite.com/magento.  I've followed the nice example at http://seconddrawer.com.au/blog/2010/01/14/simple-nginx-config-for-magento, although I haven't been able to adjust it to work in a subfolder.  

I've tried to modify the main location directive, such that it looks like
    
    location /magento {
      rewrite /magento(/index.php)?(.*) /$1 break;
      include /etc/nginx/fastcgi_params;
      fastcgi_pass   127.0.0.1:9000;
      fastcgi_param  SCRIPT_FILENAME /home/webapps/magento/index.php$1;
    }


as well as a few variations on that, but with debug output on I've seen that it only seems to modify the document_uri, not the request_uri, such that document_uri is "/" while request_uri remains "/magento".  I realize I must be missing something simple, but can anybody give any pointers on how to remove the leading "/magento" from the request_uri as well?

Thanks!
Liam
nginx 0.7.64, ubuntu 9.10

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,43760,43760#msg-43760