Re: [PATCH] push: do not add submodule odb as an alternate when recursing on demand

[Junio C Hamano <gitster@pobox.com>]

Stefan Beller <sbeller@google.com> writes:

>> Is "is it populated" a good thing to check here, though?  IIRC,
>> add-submodule-odb allows you to add the object database of an
>> inactivated submodule, so this seems to change the behaviour.  I do
>> not know if the behaviour change is a good thing (i.e. bugfix) or
>> not (i.e. regression) offhand, though.
>
> Good point, we should be able to push non-populated, even inactive(?)
> submodules. For that we strictly need add_submodule_odb here
> (or the repo object of the submodule, eventually).
>
> So let's retract this patch for now.

Not so fast.  

I am not convinced "push --recursive" should touch a submodule that
was once cloned from the upstream and then deactivated, so using
add-submodule-odb to decide if the push should go through may be a
bug that we may want to fix, in which case the diff of the patch in
question may be good as-is.  We need to sell it as a bugfix to the
users, who may complain about behaviour change (if there is one).

On the other hand, even if it were desirable for such a deactivated
submodule to be pushed, as your log message explained, there is no
reason to contaminate the in-core object hash by calling the
add-submodule-odb helper, when the only thing we care about is "do
we have the refs and object store for this submodule? we do not care
if it is activated or not".  Perhaps there is a more appropriate
helper in submodule.c that answers that question that we should be
using instead of add-submodule-odb, and if there is not yet such a
helper, perhaps this indicates that we need to add such a helper,
which essentially is the early half of what add-submodule-odb does,
i.e. ask git_path_submodule() for the object store and check if that
directory exists.

Thanks.