Ticket #13729: orderby post__in.2.diff

wp-includes/query.php

@@ -2315 +2315 @@
                         $orderby = "$wpdb->posts.post_date " . $q['order'];
                 } elseif ( 'none' == $q['orderby'] ) {
                         $orderby = '';
+                } elseif ( $q['orderby'] == 'post__in' && ! empty( $post__in ) ) {
+                        $orderby = "find_in_set(ID, '" . $post__in . "')"; 
                 } else {
                         // Used to filter values
                         $allowed_keys = array('author', 'date', 'title', 'modified', 'menu_order', 'parent', 'ID', 'rand', 'comment_count');