Fix in the case where the git branch and revision cannot be recovered.

I'm happy to accept these as additional security, but out of interest why did the Makefile attempt to set GIT_BRANCH and GIT_REVISION fail? I'd guess some issue with the git command?

It is mostly additional security.

SuperMUC does not allow connections to external repositiories so I copied all the source accross but without using the Makefile to generate the tarballs. Which is what got wrong.

mentioned in commit a6438b2f

Status changed to merged