Convert lookup_blob to struct object_id

Convert lookup_blob to take a pointer to struct object_id.

The commit was created with manual changes to blob.c and blob.h, plus
the following semantic patch:

@@
expression E1;
@@
- lookup_blob(E1.hash)
+ lookup_blob(&E1)

@@
expression E1;
@@
- lookup_blob(E1->hash)
+ lookup_blob(E1)

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http-push.c

@@ -1315,7 +1315,7 @@ static struct object_list **process_tree(struct tree *tree,
 			p = process_tree(lookup_tree(entry.oid->hash), p);
 			break;
 		case OBJ_BLOB:
-			p = process_blob(lookup_blob(entry.oid->hash), p);
+			p = process_blob(lookup_blob(entry.oid), p);
 			break;
 		default:
 			/* Subproject commit - not in this repository */