Fix GitLoaderFromArchive.
SWHLoader calls prepare(); and if prepare() fails, it calls cleanup(). However, GitLoaderFromArchive.cleanup() uses self.temp_dir and self.repo_path, so they have to be initialized.
Additionally, GitLoaderFromArchive.prepare_origin_visit does not accept the same argument name as its parent, so it fails when called by GitLoaderFromArchive.load.
Migrated from D621 (view on Phabricator)