code: function extractMetadata (content, callback) {
    var end;
    var result;
    var metadata = '';
    var body = content;
  
    // Metadata is defined by either starting and ending line,
    if (content.slice(0, 3) === '---') {
      result = content.match(/^-{3,}\s([\s\S]*?)-{3,}(\s[\s\S]*|\s?)$/);
      if (result && result.length === 3) {
        metadata = result[1];
        body = result[2];
      }
    }
    // or Markdown metadata section at beginning of file.
    else if (content.slice(0, 12) === '```metadata\n') {
      end = content.indexOf('\n```\n');
      if (end !== -1) {
        metadata = content.substring(12, end);
        body = content.substring(end + 5);
      }
    }
  
    parseMetadata(metadata, function (error, parsed) {
      if (error) return callback(error);
      callback(null, {
        metadata: parsed,
        body: body
      });
    });
  }
docs: Also from the wintersmith markdown plugin.