Joyride as alternate boot

[Bert Freudenberg]

What's the recommended best practice for alternating between stable  
and unstable builds (Update.1 and Joyride)?

We can have two builds installed at the same time, and the O game key  
toggles between both. But how do I tell olpc-update to update the  
"other" build? I can boot into Joyride, and update to Update.1, which  
makes Joyride the alternative boot, right?  But this would not  
actually patch the Update.1 to the new Update.1, but the old Joyride  
to Update.1.

Not sure I'm making myself clear, but essentially I want a cheap way  
(i.e. minimizing network traffic) to toggle between two build  
streams, updating each one separately ...

- Bert -