src/vs/workbench/browser/parts/editor/tabsTitleControl.ts/TabsTitleControl/isMoveOperation
class TabsTitleControl:	private isMoveOperation(e: DragEvent, source: GroupIdentifier) {
		const isCopy = (e.ctrlKey && !isMacintosh) || (e.altKey && isMacintosh);

		return !isCopy || source === this.group.id;
	}