Building an update center for your NetBeans Platform application with Maven is easy – simply call the nbm:autoupdate goal from the parent folder. Unless you choose another outputDirectory, the updates.xml and nbms will be available in the target/netbeans_site folder after the goal is executed.
The interesting tip is this: If you copy other nbms into that folder before running the nbm:autoupdate goal, they will be included in the updates.xml file! This is the easiest way I have found so far to combine modules from different suites into one update center. 🙂