Return an error to the caller when we can't create an object header for
some reason (printf failure) instead of simply asserting.

There's no recovery possible if we're so confused or corrupted that
we're trying to overwrite our memory.  Simply assert.

Provide error messages on hash failures: assert when given invalid
input instead of failing with a user error; provide error messages
on program errors.

It's unlikely that we'll fail to allocate a single byte, but let's check
for allocation failures for good measure.  Untangle `-1` being a marker
of not having found the hardcoded odb object; use that to reflect actual
errors.

At the moment, we're swallowing the allocation failure.  We need to
return the error to the caller.

Streaming read support for the loose ODB backend

Recursive merge: reverse the order of merge bases

config: handle CRLF-only lines and BOM