odb/source: let callers discern missing and corrupt objects

As explained in the preceding commits, reading objects can either fail
because the object truly does not exist or because it exists, but its
data is corrupt. Some callers do care about this distinction, but there
is no way to tell these two cases apart right now.

Introduce a new `ODB_READ_NOT_FOUND` value that ought to be returned by
the backends in case the object truly does not exist and adapt backends
to use it.

Note that we don't yet return this error from `odb_read_object_info()`
itself. This will be fixed in a subsequent commit.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

0 files changed, 0 insertions, 0 deletions