code: public static void addExtraHeaderToBundleManifest(File baseDir, String header, String value) throws IOException {
          Properties props = new Properties();
          File extra = new File(baseDir, EXTRA_HEADERS_FILE);
          extra.getParentFile().mkdirs();
          // If the file exist it loads it, if not nothing happens.
          props = Instructions.merge(props, extra);
          if (value != null) {
              props.setProperty(header, value);
          } else {
              props.remove(header);
          }
          FileOutputStream fos = null;
          try {
              fos = new FileOutputStream(extra);
              props.store(fos, "");
          } finally {
              IOUtils.closeQuietly(fos);
          }
      }
docs: This method is used by plugin willing to add custom header to the bundle manifest.
  
  @param baseDir the project directory
  @param header  the header to add
  @param value   the value to write
  @throws IOException if the header cannot be added