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>
diff --git a/tag.c b/tag.c
index 79b78d3..dff2516 100644
--- a/tag.c
+++ b/tag.c
@@ -142,7 +142,7 @@ int parse_tag_buffer(struct tag *item, const void *data, unsigned long size)
 	bufptr = nl + 1;
 
 	if (!strcmp(type, blob_type)) {
-		item->tagged = &lookup_blob(oid.hash)->object;
+		item->tagged = &lookup_blob(&oid)->object;
 	} else if (!strcmp(type, tree_type)) {
 		item->tagged = &lookup_tree(oid.hash)->object;
 	} else if (!strcmp(type, commit_type)) {