Patch Set 1: I would prefer that you didn't submit this

This change is *almost* ready for review. Currently I see four things to improve/work on:
* GitSyncInfo class
* GitResourceVariantComparator
* handle multiple merge base points in GitBaseResourceVariant
* fix test cases

I'll send mail on jgit dev list with detailed description of first three points. Sending this to gerrit will make discussion easier ;)