       parent: parent
       position: position
       oldParent: oldParent
+      oldIndex: oldIndex
     if importing
       #cmsg = Messages.findOne child
       doc.updator = cmsg.creator

          $set: root: root ? child  ## actually must be root
        ,
          multi: true
      _submessagesChanged cmsg.root     ## old root
      _submessagesChanged root ? child  ## new root
    doc =

    root = null
  if canEdit(child) and canPost group, parent
    cmsg = Messages.findOne child
    oldIndex = null
    if oldParent
      oldParent = findMessageParent child
      if oldParent?
        oldIndex = oldParent.children.indexOf child
        Messages.update oldParent._id,
          $pop: children: child
    if parent?
