class Sinatra::Default

def send_file(path, opts={})

TODO deprecation warning for :disposition argument.
--
setting the Content-Transfer-Encoding header is deprecated.
The :disposition option is deprecated; use: #attachment. This method 
def send_file(path, opts={})
  opts[:disposition] = 'attachment' if !opts.key?(:disposition)
  attachment opts[:filename] || path if opts[:filename] || opts[:disposition]
  response['Content-Transfer-Encoding'] = 'binary' if opts[:disposition]
  super(path, opts)
end