copy: true behavior is buggy.

I encountered a bug when using copy: true. If you drop something, it will be created twice. I think this is because the model is changed and the gu-transit element is inserted as well. That’s why we then have two occurences of the same object, while only one of them is linked to the model

demo: http://46bb3f4c.ngrok.io/

If you point me in the right direction, that would be great and I will submit a PR. Thanks ahead.

[Astray-git]

Thanks for the vue issue, we should let vue handle DOM update. I cancelled dragula DOM actions.

[nblackburn]

@FranzSkuffka Workaround for the duplicate drop error:

instance.on('drop', (element, target, origin) => {

    const isCopy = dragElement !== dropElement;

    if (isCopy && target.contains(element)) {
        element.remove();
    }
});