Merge branch 'ps/object-store'

Merge branch 'ps/object-store'

Code clean-up around object access API.

* ps/object-store:
  odb: rename `read_object_with_reference()`
  odb: rename `pretend_object_file()`
  odb: rename `has_object()`
  odb: rename `repo_read_object_file()`
  odb: rename `oid_object_info()`
  odb: trivial refactorings to get rid of `the_repository`
  odb: get rid of `the_repository` when handling submodule sources
  odb: get rid of `the_repository` when handling the primary source
  odb: get rid of `the_repository` in `for_each()` functions
  odb: get rid of `the_repository` when handling alternates
  odb: get rid of `the_repository` in `odb_mkstemp()`
  odb: get rid of `the_repository` in `assert_oid_type()`
  odb: get rid of `the_repository` in `find_odb()`
  odb: introduce parent pointers
  object-store: rename files to "odb.{c,h}"
  object-store: rename `object_directory` to `odb_source`
  object-store: rename `raw_object_store` to `object_database`