Commit a5c1780a0355a71b9fb70f1f1977ce726ee5b8d8 sets the pack_id of existing
objects to MAX_PACK_ID. When the same object is referenced later again it is
found in the local object hash. With such a pack_id fast-import should not try
to locate that object in the newly created pack(s).
Signed-off-by: Simon Hausmann <simon@lst.de> Signed-off-by: Shawn O. Pearce <spearce@spearce.org>