'Add a new thin pack to this object store.
Thin packs are packs that contain deltas with parents that exist
outside the pack. They should never be placed in the object store
directly, and always indexed and completed as they are copied.
:param read_all: Read function that blocks until the number of
requested bytes are read.
:param read_some: Read function that returns at least one byte, but may
not return the number of bytes requested.
:return: A Pack object pointing at the now-completed thin pack in the
objects/pack directory.'

def add_thin_pack(self, read_all, read_some):

    (fd, path) = tempfile.mkstemp(dir=self.path, prefix='tmp_pack_')
    with os.fdopen(fd, 'w+b') as f:
        indexer = PackIndexer(f, resolve_ext_ref=self.get_raw)
        copier = PackStreamCopier(read_all, read_some, f, delta_iter=indexer)
        copier.verify()
        return self._complete_thin_pack(f, path, copier, indexer)
