title: EntityManager.refresh detached entity throws exception why in your opinion?
body: <p>I understand that the <code>JPA</code> specifications mandates that if a detached entity is passed to the <code>entityManager.refresh()</code> then an <code>IllegalArgumentException</code> shall be thrown, but I don't understand why? The meaning of the refresh method is ignore any changes done and give 
  me a fresh new copy from the DB. </p>