I understand WP 3.6 has changed to have a revision with same content as a current post. It seems that WP 3.6 updates a current post record first and copies it as a revision next. It works fine when I first publish posts in WP 3.6.
But if I update an existing post from WP 3.5, content before update will be lost because WP 3.6 would update it before copy it and no revision with same content is there. I believe it's needed to take care of it. But I couldn't find code for this purpose. Is there?