-Added subproject support for addProjectLabel:w
Avoid NullPointerException
Contributions from Christian Buerenheide
JENKINS-21350: Here we get a NullPointerException when checking out a variant project where the original project has been moved. In my opinion this is a major problem and it would be good to have it fixed in one of the next plugin versions.
JENKINS-21351: This is just a nice-to-have. A little inconsistency since Groovy expressions can be used in the main SCM config section but not in the checkin post-build action.
JENKINS-21370: The addprojectlabel functionality had been removed with 1.20. This feature has been recovered and extended with the functionality to recurse subprojects for applying checkpoint labels to subprojects as well.

Additionally, fixed:
JENKINS-21410: memory leak in Plugin 1.20
Fixed issue when moved files are fetched from server
[maven-release-plugin] prepare release integrity-plugin-1.21