anchor.diff:      /// the enqueued changes.
       /// </summary>
       member x.Commit() =
  +        let top = isTopLevel.Value
  +        isTopLevel.Value <- false
  +
  +
           // cache the currently running transaction (if any)
           // and make tourselves current.
           let old = running.Value
  
positive.code:         // when the commit is over we restore the old
          // running transaction (if any)
          running.Value <- old
  
  /// <summary>
  /// defines a base class for all adaptive objects implementing
  
negative.code:     let outputs = WeakSet<IAdaptiveObject>() :> ICollection<_>
      let callbacks = ConcurrentHashSet<unit -> unit>() :> ICollection<_>
  
      static let time = AdaptiveObject() :> IAdaptiveObject
  
      static member Time = time
  