code: private void addResourcesFromFolder( ApkBuilder builder,  File folder )
              throws SealedApkException, DuplicateFileException, ApkCreationException, IOException
      {
          final int folderPathLength = folder.getCanonicalPath().length();
  
          final List<File> resourceFiles = new ArrayList<>(  );
          collectFiles( folder, resourceFiles );
  
          for ( final File resourceFile : resourceFiles )
          {
              final String resourceName = resourceFile
                      .getCanonicalPath()
                      .substring( folderPathLength + 1 )
                      .replaceAll( "\\\\", "/" );
              getLog().info( "Adding resource " + resourceFile + " : " + resourceName );
              builder.addFile( resourceFile,  resourceName );
          }
      }
docs: Adds all non-class files from folder, so that we can add META-INF/services resources.