For information about the project, see http://jpilgrim.github.io/eclipsetools/j2og/
In order to create the update site, simply run
mvn clean install
The new update site will be created in j2og/releng/de.jevopi.j2og.updatesite/target
In order to update the version number (of everything), run
mvn org.eclipse.tycho:tycho-versions-plugin:set-version -DnewVersion="x.y.z"