Merging between layers throws unnecessary conflicts for objects with placeholder IDs

[Ldp]

1. Open JOSM, create 2 layers
2. Create a node or way in 1 layer, merge it to the other layer, and delete the node or way in the originating layer.
3. Go to the second layer, select the node, and merge it back to the first layer.

This results in a conflict, but the conflict doesn't show up in the Conflict List.

Two things:

1. These actions should not result in a conflict. While merging objects to another layer, even if they have been in that layer before but since deleted, and when they have placeholder IDs, treat them as fresh objects in the destination layer.
2. If a conflict is thrown anyway, at least show it in the list.

Tested with 2962, but present for as long as I can remember, really.

[mjulius]

The conflict should show up in the list once you switch back to the first layer. It won't be visible while the second layer is active.

[Ldp]

Replying to mjulius:

The conflict should show up in the list once you switch back to the first layer. It won't be visible while the second layer is active.

Of course, missed that.

The way to circumvent the conflicts is to save the first layer and then reopen. You can then safely merge back the object. As you mentioned in your mail to josm-dev, the deleted object isn't saved, so there is no conflict to throw.

[mjulius]

(In [3039]) fixes #4522 - Merging between layers throws unnecessary conflicts for objects with placeholder IDs

ignore deleted new primitives when merging