This change was neccessary as git-describe only can track tags, and the 0.4.12 release was a non-linear one, with the 0.4.12 tag being on its own branch.
Two things changed for the "outside":
1. Workspaces with changes don't have a "-dirty" appended anymore. This can be added later, however.
2. The commit that represents a version change on the master branch has now to be set manually inside the CMakeLists.txt