Patch Set 5: Looks good to me, but someone else must approve; IP review completed

Ok good for me know. Could be merged now.

One leftover we have. Your modifications are still not covered by unit tests. Since we didn't copied the class but only enhanced a already well tested class that's not as bad as with a copy. But of course we need also tests for incore mergers. Tests which check whether the merge succeeds in bare repos, whether we correctly write merged content although we don't have our standard file-system-location to persist new content, and so on.

You decide - in this commit or in a follow up?