Jetty provides capability to deploy an arbitrary context or web application by monitoring a directory for changes. If a web application or a context descriptor is added to the directory, a new context will be deployed. If a context descriptor is touched/updated then it's context will be stopped, reconfigured and redeployed. If a context descriptor is removed, then it's context will be stopped and removed from the server.
The documentation for Deployment Manager, WebAppProvider, and ContextProvider is forthcoming.