Merge branch 'jt/pretend-object-never-come-from-elsewhere'

The pretend-object mechanism checks if the given object already exists in the object store before deciding to keep the data in-core, but the check would have triggered lazy fetching of such an object from a promissor remote. * jt/pretend-object-never-come-from-elsewhere: sha1-file: make pretend_object_file() not prefetch