upload-pack.c: treat want-ref relative to namespace

When 'upload-pack' runs within the context of a git namespace, treat any
'want-ref' lines the client sends as relative to that namespace.

Also check if the wanted ref is hidden via 'hideRefs'. If it is hidden,
respond with an error as if the ref didn't exist.

Helped-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Kim Altintop <kim@eagain.st>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/upload-pack.c b/upload-pack.c
index 297b76f..6ce0723 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -1417,21 +1417,25 @@ static int parse_want_ref(struct packet_writer *writer, const char *line,
 			  struct string_list *wanted_refs,
 			  struct object_array *want_obj)
 {
-	const char *arg;
-	if (skip_prefix(line, "want-ref ", &arg)) {
+	const char *refname_nons;
+	if (skip_prefix(line, "want-ref ", &refname_nons)) {
 		struct object_id oid;
 		struct string_list_item *item;
 		struct object *o;
+		struct strbuf refname = STRBUF_INIT;
 
-		if (read_ref(arg, &oid)) {
-			packet_writer_error(writer, "unknown ref %s", arg);
-			die("unknown ref %s", arg);
+		strbuf_addf(&refname, "%s%s", get_git_namespace(), refname_nons);
+		if (ref_is_hidden(refname_nons, refname.buf) ||
+		    read_ref(refname.buf, &oid)) {
+			packet_writer_error(writer, "unknown ref %s", refname_nons);
+			die("unknown ref %s", refname_nons);
 		}
+		strbuf_release(&refname);
 
-		item = string_list_append(wanted_refs, arg);
+		item = string_list_append(wanted_refs, refname_nons);
 		item->util = oiddup(&oid);
 
-		o = parse_object_or_die(&oid, arg);
+		o = parse_object_or_die(&oid, refname_nons);
 		if (!(o->flags & WANTED)) {
 			o->flags |= WANTED;
 			add_object_array(o, NULL, want_obj);