object: stop depending on `the_repository`

object: stop depending on `the_repository`

There are a couple of functions exposed by "object.c" that implicitly
depend on `the_repository`. Remove this dependency by injecting the
repository via a parameter. Adapt callers accordingly by simply using
`the_repository`, except in cases where the subsystem is already free of
the repository. In that case, we instead pass the repository provided by
the caller's context.

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