src/vs/platform/undoRedo/common/undoRedoService.ts/UndoRedoService/_workspaceUndo
class UndoRedoService:	private _workspaceUndo(strResource: string, element: WorkspaceStackElement, undoConfirmed: boolean): Promise<void> | void {
		const affectedEditStacks = this._getAffectedEditStacks(element);
		const verificationError = this._checkWorkspaceUndo(strResource, element, affectedEditStacks, /*invalidated resources will be checked after the prepare call*/false);
		if (verificationError) {
			return verificationError.returnValue;
		}
		return this._confirmAndExecuteWorkspaceUndo(strResource, element, affectedEditStacks, undoConfirmed);
	}