http: use struct object_id instead of bare sha1

The dumb-http walker code still passes around and stores object ids as
"unsigned char *sha1". Let's modernize it.

There's probably still more work to be done to handle dumb-http fetches
with a new, larger hash. But that can wait; this is enough that we can
now convert some of the low-level object routines that we call into from
here (and in fact, some of the "oid.hash" references added here will be
further improved in the next patch).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/http-walker.c b/http-walker.c
index 0a392c8..856716c 100644
--- a/http-walker.c
+++ b/http-walker.c
@@ -58,7 +58,7 @@ static void start_object_request(struct walker *walker,
 	struct active_request_slot *slot;
 	struct http_object_request *req;
 
-	req = new_http_object_request(obj_req->repo->base, obj_req->oid.hash);
+	req = new_http_object_request(obj_req->repo->base, &obj_req->oid);
 	if (req == NULL) {
 		obj_req->state = ABORTED;
 		return;
@@ -543,11 +543,11 @@ static int fetch_object(struct walker *walker, unsigned char *sha1)
 	} else if (req->zret != Z_STREAM_END) {
 		walker->corrupt_object_found++;
 		ret = error("File %s (%s) corrupt", hex, req->url);
-	} else if (!hasheq(obj_req->oid.hash, req->real_sha1)) {
+	} else if (!oideq(&obj_req->oid, &req->real_oid)) {
 		ret = error("File %s has bad hash", hex);
 	} else if (req->rename < 0) {
 		struct strbuf buf = STRBUF_INIT;
-		loose_object_path(the_repository, &buf, req->sha1);
+		loose_object_path(the_repository, &buf, req->oid.hash);
 		ret = error("unable to write sha1 filename %s", buf.buf);
 		strbuf_release(&buf);
 	}