Patch Set 2:

I think this change breaks Gerrit Code Review when branch level permissions are used. IIRC, Gerrit uses ObjectWalk to enumerate the set of objects that would have been considered in the edge set for delta bases, but in this change I stripped that code out of ObjectWalk and moved it all into PackWriter. This prevents the client from using any file or tree as a delta base for a REF_DELTA, resulting in Gerrit rejecting the pack file.

I guess I need to decide if I should restore this behavior to ObjectWalk, or put it into Gerrit itself. Its unlikely an application needs the UNINTERESTING tree and blob objects, so its not really worth having in the core JGit library, and especially not by default given how expensive this is to compute. So it seems reasonable to me to require the application to contain this logic itself... and thus I need to fix Gerrit when I upgrade Gerrit to use a JGit 0.11.1 or later.