code: function getNew(body) {
        // If we haven't already cleared the callback (we got the body, then the
        // message on the subscriber)
        if (timer) {
          // If the new body is present (say, if it wasn't deleted)
          if (body) {
            // Calculate the new Etag
            ourEtag = '"' + sha1hex(body) + '"';
  
            // If it's a new body (which it almost certainly should be)
            if (ourEtag != theirEtag) {
              sendNewEtagAndBody(body);
            }
            // If it's not a new body we do nothing and keep listening / waiting
  
          // If the new body is empty
          } else {
            // Respond that it is now Not Found
            respondNotFound();
          }
        }
      }
docs: Callback for when we get a mesage that there's a new body.