Eclipse Tycho: Disable p2 dependency resolution with tycho.mode=maven

In Eclipse Tycho based builds the first step is always computation of the target platform and depedency resolution. This takes quite some time and in certain use cases it is not necessary. Typical use cases are updating versions with the tycho-versions-plugin, or displaying the effective pom with help:effective-pom.

The p2 target platform & dependency resolution can be skipped by setting the tycho-mode system property:

mvn -Dtycho.mode=maven <goals>

This useful feature is a bit hidden in just a few posts, e.g. https://www.eclipse.org/lists/tycho-user/msg06439.html.