anchor.diff:          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)    
  
positive.code:     |> Seq.map (function
                  | "**" -> Recursive
                  | a when a = filePattern -> FilePattern(a)
                  | a -> Directory(a))
      |> Seq.toList
      |> buildPaths [baseDir]
  
negative.code: open System.Collections.Generic
  open System.IO
  open Fake
  open System.Text.RegularExpressions
  
  type private SearchOption = 
  | Directory of string
  