anchor.diff:  
       member this.IsHead = isHead
   
  -    member this.Bookmarks : Bookmark set = 
  +    member this.Bookmarks : Bookmark set =
           collectBookmarks()
   
       static member (-) (ref : Baseline, target : Baseline) : Bookmark set =
  
positive.code:         let branch = tag.Substring(0, idx)
          let version = tag.Substring(idx+1)
          { TagInfo.BuildBranch = branch; TagInfo.BuildNumber = version }
          
  
  // =====================================================================================================
  
  
negative.code: 
  // =====================================================================================================
  
  [<Sealed>]
  type Factory(graph : Graph) = class end
  with
      let wsDir = Env.GetFolder Env.Folder.Workspace
  