The LFS batch and upload handlers linked an object that already existed
in the content store but was not linked to the current repo whenever the
token's user could access it in another repo. Deploy-key tokens carry
the repo owner's identity, so a single-repo write deploy key could link
and then download objects from any repo the owner can see.
This drops the cross-repo access check: the batch handler now makes the
client upload (hash-verified) any object not yet linked to the repo, and
the upload handler skips proof of possession only when the object is
already linked to the current repo.
66a3723cbb