anchor.diff:          }
         });
   
  +      // Download all the packages in parallel; also, failure to download some
  +      // don't affect the others.
         return Future.wait(futures);
       });
     }
  
positive.code:     final List<int> cleansedBytes = bytes.map((b) => b & 0xff).toList();
      final arc.Archive archive =
          new arc.ZipDecoder().decodeBytes(cleansedBytes, verify: false);
      return Future.forEach(archive.files, (arc.ArchiveFile file) {
        _writeArchiveFile(file, dir);
      });
  
negative.code:     if (file.size == 0 && file.name.endsWith('/')) {
        // GitHub archives always contain a top level directory named
        // <package_name>-<branch>. We're not interested in it.
        // We also don't have to create any sub-directories: [_writeFile] will.
        return new Future.value();
      } else {
        // Same as above: strip the top level directory from the file name.
  