How to start the Jetty server when using Scalatra with SBT

When working on a Scalatra project, this is how I start the Jetty server using SBT:

# (1) start sbt
$ sbt

# (2) start the jetty server at the sbt command line
> container:start

There is supposed to be a way to get this to be a "continuous compile", so you don't always have to stop and start Jetty, but I haven't been able to get that to work properly.