Merge branch 'jt/add-submodule-odb-clean-up'

More code paths that use the hack to add submodule's object database to the set of alternate object store have been cleaned up. * jt/add-submodule-odb-clean-up: revision: remove "submodule" from opt struct repository: support unabsorbed in repo_submodule_init submodule: remove unnecessary unabsorbed fallback