anchor.diff:      static member Parse(s : string) = 
           match s with 
           | "encrypt" -> ok Encrypt
  -        | "plaintext" -> ok  Plaintext
  +        | "plaintext" -> ok Plaintext
           | "selective" -> ok Selective
           | _ ->  InvalidCredentialsMigrationMode s |> fail
   
  
positive.code:             |> List.map (fun (key,value) -> key, (String.quoted value, getAuth key))
              |> Map.ofList
          
          { PackageSources = if clearSources then sources
                             else 
                                Map.fold 
                                  (fun acc k v -> Map.add k v acc)
                                  nugetConfig.PackageSources
                                  sources
                             |> Map.filter (fun k _ -> Set.contains k disabledSources |> not)
            PackageRestoreEnabled = 
              match configNode |> getNode "packageRestore" |> Option.bind (tryGetValue "enabled") with
              | Some value -> bool.Parse(value)
  
negative.code:             | true -> ConfigAuthentication(username, password)
              | false -> PlainTextAuthentication(username, password)
          | _ -> failwith "invalid auth"
  
  /// Represents type of NuGet packages.config file
  type NugetPackagesConfigType = ProjectLevel | SolutionLevel
  
  