/**
   require() plugin which returns a db handle for the checkout db for
   Fossil.require's shared Fossil.Context. If no checkout has been
   opened when this is called, openCheckout() is called on the
   context, otherwise there are no side effects.
*/
return requireS2(['fsl/context'], proc(F){
  return F.hasDb('checkout') ||| F.openCheckout().db;
});
