Copying list items from other list but should create new scope or watch

[MBing]

I have this case where I am using a main list with subitems and when you click a main item you get its subitems who should be draggable.
http://plnkr.co/edit/6s03Gq

It's hard to explain exactly everything, so I made this plunkr and if you follow these steps you will see the problem:

• Drag the first 'subitem 0_0' down below 'subitem 0_1'
• Click 'Main item 1'
  • Drag the first item 'subitem 1_1' down to any other place
    --> You will see it not only took this item. but you will also have a subitem from the previous list being attached to it 'subitem 0_0'.

[MBing]

I changed ng-repeat="subItem in currentMainItem.subItems track by $index" to
ng-repeat="subItem in currentMainItem.subItems"

and it all worked fluently!
So closing this and plunker is updated.