anchor.diff:              for p in g.Value.NugetPackages do
                   let k = g.Key,p.Name
                   if usedPackages.ContainsKey k then
  -                    failwithf "Package %O is referenced more than once in %s (group %O)" p.Name referencesFile.FileName g.Key
  +                    failwithf "Package %O is referenced more than once in %s within group %O." p.Name referencesFile.FileName g.Key
                   usedPackages.Add(k,p)
   
           for g in referencesFile.Groups do
  
positive.code:         Set.union fromNuGets fromSourceFiles
  
      member this.GetTopLevelDependencies(groupName) = 
          let group = groups.[groupName]
          let transitive = this.GetTransitiveDependencies groupName
  
          group.Resolution
          |> Map.filter (fun name _ -> transitive.Contains name |> not)
  
      member this.GetGroupedResolution() =
          this.Groups
  
negative.code:             for p in g.NugetPackages do
                  let k = groupName,p.Name
                  if usedPackages.ContainsKey k then
                      failwithf "Package %O is referenced more than once in %s within group %O." p.Name referencesFile.FileName groupName
                  usedPackages.Add(k,p)
  
              g.NugetPackages
  