test_pack_repository does not test 2a
Beyond simply adding 2a to the scenario list and making the tests pass, there's a couple of issues here:
- the scenario list weirdly duplicates a bunch of information that could be much more simply plucked from format objects. (i.e. why not define the scenarios by bzrdir_format registry names only, and automatically derive the attributes from there?)
- perhaps there should not be a manual scenario list at all, ideally we should generate it from the complete list of formats, like per_repository_
i.e. it would be good to not just fix the immediate bug, but try to fix what allowed it to happen in the first place.