submodule update: test recursive path reporting from subdirectory
This patch is just a test and fixes no bug as there is currently no bug
in the path handling of `submodule update`.
In `submodule update` we make a call to `submodule--helper list --prefix
"$wt_prefix"` which looks a bit brittle and likely to introduce a bug
for the path handling. It is not a bug as the prefix is ignored inside
the submodule helper for now. If this test breaks eventually, we want
to make sure the `wt_prefix` is passed correctly into recursive submodules.
Hint: In recursive submodules we expect `wt_prefix` to be empty.
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>