When a thin pack wants to send a tree object at "sub/dir", and
the commit that is common between the sender and the receiver
that is used as the base object has a subproject at that path,
we should not try to use the data at "sub/dir" of the base tree
as a tree object. It is not a tree to begin with, and more
importantly, the commit object there does not have to even
exist.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
