Do not change source object order when coping

[pawel-kordowski]

In case when order_with_respect_to used and model instance copied by means of setting model_object.pk = None with changed wrt value, objects with the original wrt above got reordered.

Currently there are 2 possible workarounds:

• set model_objects.order = None but it leads to an extra db query to set order
• use bulk_create

[shuckc]

The technique you've linked to isn't something I've been aware of. Surprisingly to see it documented - it's not at all nice reflected by the number of caveats in the docs.

I'll add a comment in the code to link to the docs, but this looks fine.

[shuckc]

There's a problem demonstrated by 9fb8dc6 - q2_a3 has a duplicate order
If the user makes a copy without changing an ORT field, a new increased order value is required.