anchor.diff:  open System.Collections.Generic
   open System.IO
   open Fake
  +open System.Text.RegularExpressions
   
   type private SearchOption = 
   | Directory of string
  
positive.code:     |> Seq.map (function
                  | "**" -> Recursive
                  | a when a = filePattern -> FilePattern(a)
                  | a -> Directory(a))
      |> Seq.toList
      |> buildPaths [baseDir]
  
negative.code:         Seq.collect (fun dir -> Directory.EnumerateFiles(dir, pattern)) acc
          |> Seq.toList
           
  let private isDrive =
      let regex = Regex(@"^[A-Za-z]:$", RegexOptions.Compiled)
      fun dir -> regex.IsMatch dir
  
  let private search (baseDir:string) (input : string) =
      let input = input.Replace(baseDir,"")
      let filePattern = Path.GetFileName(input)    
  