Code review comment for lp:~gary/bzr/bug835035

Thanks for reminding me about the test. To make it a bit better:

1) This should be a bzrlib/tests/per_repository_reference test, because repositories that support "references" are the ones that refer to stacked locations. (I'm not super happy that it isn't per_repository_fallback or whatever.)

2) Can we not hard-code the stacked-on format (format="2a"), and instead use either pack-0.92 which doesn't support stacking at all, or if you need one that supports stacking, but an incompatible serializer, then you can say something like:

if self.repository_format.? == "2a":
  fallback_format = "1.9"
else:
  fallback_format = "2a"

I think that will cover your XXX better. It will allow new implementations to also get tested, and still allow you to have full coverage, including Remote repositories, etc.