Exhaustively test for how combining various "mixed-level" "git
submodule" option works. "Mixed-level" here means options that are
accepted by a mixture of the top-level "submodule" command, and
e.g. the "status" sub-command.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
