anchor.diff:    name = attrs.name or "${namePrefix}${gemName}-${version}";
   
     inherit src;
  +
   
     unpackPhase = attrs.unpackPhase or ''
       runHook preUnpack
  
positive.code:       gempkg=$(echo "$output" | grep -oP 'File: \K(.*)')
  
        echo "gem package built: $gempkg"
      fi
  
      runHook postBuild
  
negative.code:     else if type == "git" then
        fetchgit {
          inherit (attrs.source) url rev sha256 fetchSubmodules;
        }
      else if type == "url" then
        fetchurl attrs.source
  