class Rake::Application

def have_rakefile

If a match is found, it is copied into @rakefile.
True if one of the files in RAKEFILES is in the current directory. 
def have_rakefile
  @rakefiles.each do |fn|
    if File.exist?(fn)
      others = Rake.glob(fn, File::FNM_CASEFOLD)
      return others.size == 1 ? others.first : fn
    elsif fn == ''
      return fn
    end
  end
  return nil
end