class RDoc::Markup::PreProcess

def find_include_file(name)
  to_search = [File.dirname(@input_file_name)].concat @include_path
  to_search.each do |dir|
    full_name = File.join(dir, name)
    stat = File.stat(full_name) rescue next
    return full_name if stat.readable?
  end
  nil
end