I missed this during a refactor and there wasn't test coverage.
Instead of adding more heavy-weight integration tests, I tried
to use `gomock` here to assert on the options objects after CLI
flag parsing. I think with a few more helpers, this could be a
good way to get a lot more combinations covered without adding
a ton of slow E2E tests.
Signed-off-by: Milas Bowman <milas.bowman@docker.com>
