anchor.diff:  open System
   open System.IO
   
  -type Project(currentFile:string, filesAndContents:(string * string option) array) as self =
  +type Project(currentFile:string, filesAndContents:(string * string option) array, updatedFiles:Set<string>) as self =
       let currentFile = Path.GetFullPath currentFile
       let getIndex fileName = Seq.findIndex ((=) fileName) self.Files
  +    
  +    new(currentFile:string, filesAndContents:(string * string option) array) =
  +        Project(currentFile, filesAndContents, Set.empty)
   
       new(source:string, fileName:string) =
           Project(fileName, [|fileName, Some source|])
  
positive.code:         let index = getIndex fileName
          let filesAndContents = Array.copy filesAndContents
          Array.set filesAndContents index (fileName, Some contents)
          new Project(currentFile, filesAndContents)
      member self.UpdateCurrentFileContents contents =
          self.UpdateContents self.CurrentFile contents
negative.code:     member self.CurrentFile with get() = currentFile
      member self.FileContents = Array.map snd filesAndContents
      member self.CurrentFileContents = self.GetContents self.CurrentFile
      member self.UpdatedFiles = updatedFiles
      
      member self.FilesInScope fileName =
          let fileName = Path.GetFullPath fileName
  