blob: add repository argument to lookup_blob

Add a repository argument to allow the callers of lookup_blob
to be more specific about which repository to act on. This is a small
mechanical change; it doesn't change the implementation to handle
repositories other than the_repository yet.

As with the previous commits, use a macro to catch callers passing a
repository other than the_repository at compile time.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

list-objects.c

@@ -167,7 +167,7 @@ static void process_tree(struct rev_info *revs,
 					cb_data);
 		else
 			process_blob(revs,
-				     lookup_blob(entry.oid),
+				     lookup_blob(the_repository, entry.oid),
 				     show, base, entry.path,
 				     cb_data, filter_fn, filter_data);
 	}