Re: [PATCH 6/7] read-cache: refuse to create index referring to external objects

On Sat, Jan 26, 2013 at 2:00 AM, Junio C Hamano [off-list ref] wrote:

This is not a tangent, but if you want to go this "forbid making our
repository depend on objects we do not have but we know about after
we peek submodule odb" route [*1*], write_sha1_file() needs to be
told about has_sha1_file_proper().  We may "git add" a new blob in
the superproject, the blob may not yet exist in *our* repository,
but may happen to already exist in the submodue odb.  In such a
case, write_sha1_file() has to write that blob in our repository,
without the existing has_sha1_file() check bypassing it.  Otherwise
our attempt to create a tree that contains that blob will fail,
saying that the blob only seems to exist to us via submodule odb but
not in our repository.

Another thing needs to be done for this to work. The current reading
order is packs first, loose objects next. If we create a local loose
duplicate of an alternate packed object, our local version will never
be read. Regardless the submodule odb issue, I think we should prefer
reading local loose objects over alternate packed ones.
-- 
Duy