This addresses a long-standing TODO where `complete -C` output isn't
deduplicated.
With this patch, the same deduplication and sort procedure that is run on actual
pager completions is also executed for `complete -C` completions (with a `-C`
payload specified).
This makes it possible to use `complete -C` to test what completions will
actually be generated by the completions pager instead of it displaying
something completely divorced from reality, improving the productivity of fish
completions developers.
Note that completions that wouldn't be shown in the pager are also omitted from
the results, e.g. `test/buildroot/` and `test/fish_expand_test/` are omitted
from the check matches in `checks/complete_directories.fish` because even if
they were generated, the pager wouldn't have shown them. This again makes
reasoning about and debugging completions much easier and more sane.
We have now entirely switched the script tests to littlecheck.
Note: This adjusts the complete_directories test, because it removes a
directory that was created before by a .in test. There's no real
change in behavior.
This does require the test directory be cleaned, or the tests will fail.
test_util gets to stay for a while longer, because it sets up the
testing env (locale and such).
