At the same time, we change the defaults for both of them to "date" (they were
"recency" and "alphabetical", respectively, before). This is the reason we need
to touch so many integration tests. For some of them I decided to adapt the test
assertions to the changed sort order; for others, I added a SetupConfig step to
set the order back to "recency" so that I don't have to change what the test
does (e.g. how many SelectNextItem() calls are needed to get to a certain
branch).
We allow deleting remote branches (or local and remote branches) only if *all*
selected branches have one.
We show the a warning about force-deleting as soon as at least one of the
selected branches is not fully merged.
The added test only tests a few of the most interesting cases; I didn't try to
cover the whole space of possible combinations, that would have been too much.
