Blender Git Loki

Fix T74649: Outliner: Cannot set/clear parent with 'Keep Transforms'

Parenting in the outliner via drang and drop would always happen without
the 'Keep Transforms' option. Since this is often desired, this adds the
ability to hold Alt for doing this to the drop action.

Adding the hint to hold Alt to the operator name is not nice, but since
the operator name is used for the UI, there doesnt seem to be a nicer
way of doing this.

If modifier keys are needed back for other actions, spawning a menu
instead could be an alternative for the future.

Maniphest Tasks: T74649

Differential Revision: https://developer.blender.org/D7120