We can already do this:

./jbdevstudio -vmargs -Djboss.discovery.directory.url=http://www.qa.jboss.com/binaries/RHDS/builds/staging/devstudio-5.0_trunk.updatesite/product/devstudio-directory.xml

But the URL hard-coded in the discovery plugin's plugin.xml [1] will need to change during QE testing for a milestone release, since the site on which the JBDS SOA bits reside will be a different URL from where they'll end up when published to Early Access or once GA'd.

So, we need something like this:

./jbdevstudio -vmargs -Djboss.soa.update.url=http://devstudio.jboss.com/updates/5.0/staging/soa-tooling/

and that there's a ${jboss.soa.update.url} variable in the plugin.xml of the discovery plugin [1], which would be set to a default value of http://devstudio.jboss.com/updates/5.0/soa-tooling/ in plugin.properties [2]

[1] https://svn.jboss.org/repos/devstudio/trunk/product/plugins/com.jboss.jbds.central.discovery/plugin.xml
[2] https://svn.jboss.org/repos/devstudio/trunk/product/plugins/com.jboss.jbds.central.discovery/plugin.properties