anchor.diff:      ResolvedSourceFiles : ModuleResolver.ResolvedSourceFile list }
   
   type UpdateMode =
  -    | UpdatePackage of  GroupName * PackageName
  +    | UpdatePackage of GroupName * PackageName
       | UpdateGroup of GroupName
       | Install
       | UpdateAll
  
positive.code: let allPrereleases versions = versions |> List.filter (fun v -> v.PreRelease <> None) = versions
  
  let cleanupNames (model : PackageResolution) : PackageResolution = 
      model |> Seq.fold (fun map x -> 
                   let package = x.Value
                   let cleanup = 
                       { package with Dependencies = 
                                          package.Dependencies 
                                          |> Set.map (fun (name, v, d) -> model.[name].Name, v, d) }
                   Map.add package.Name cleanup map) Map.empty
  
  [<RequireQualifiedAccess>]
  type Resolution =
  
negative.code:             | true,Resolution.Conflict(_) -> tryToImprove true |> snd
              | _,x-> x
  
      step (Map.empty, [], Set.empty, rootDependencies)