object: convert lookup_unknown_object() to use object_id

There are no callers left of lookup_unknown_object() that aren't just
passing us the "hash" member of a "struct object_id". Let's take the
whole struct, which gets us closer to removing all raw sha1 variables.
It also matches the existing conversions of lookup_blob(), etc.

The conversions of callers were done by hand, but they're all mechanical
one-liners.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

object.h

@@ -143,7 +143,7 @@ struct object *parse_object_or_die(const struct object_id *oid, const char *name
 struct object *parse_object_buffer(struct repository *r, const struct object_id *oid, enum object_type type, unsigned long size, void *buffer, int *eaten_p);
 
 /** Returns the object, with potentially excess memory allocated. **/
-struct object *lookup_unknown_object(const unsigned  char *sha1);
+struct object *lookup_unknown_object(const struct object_id *oid);
 
 struct object_list *object_list_insert(struct object *item,
 				       struct object_list **list_p);