anchor.diff:  
   procedure TAbGzipArchive.SetTarAutoHandle(const Value: Boolean);
   begin
  -  case Value of
  -    True  : begin
  -      SwapToTar;
  -    end;
  -
  -    False : begin
  -      SwapToGzip;
  -    end;
  -  end;
  +  if Value then
  +    SwapToTar
  +  else
  +    SwapToGzip;
     FTarAutoHandle := Value;
   end;
   
  
positive.code:   Result := 0;
  end;
  
  function TAbGzipItem.GetExtraField: string;
  begin
    Result := '';
    if HasExtraField then begin
      SetLength(Result, FXLen);
      Move(FExtraField, Result[1], FXLen);
    end;
  end;
  
  function TAbGzipItem.GetFileComment: string;
  begin
    Result := '';
    if HasFileComment then
      Result := FFileComment;
  end;
  
  
  function TAbGzipItem.GetFileSystem: TAbGzFileSystem;
  begin
    case FGzHeader.OS of
  
negative.code:       read FGZHeader.Flags write FGZHeader.Flags;
  
      property FileComment : string
        read FFileComment write SetFileComment;
  
      property FileSystem : TAbGzFileSystem {Default: osFat (Windows); osUnix (Linux)}
        read GetFileSystem write SetFileSystem;
  
      property ExtraField : string
        read FExtraField write SetExtraField;
  
      property HeaderCRC : Word
        read GetHeaderCRC;
  