===== Summary

Strips the extension from the requested path (env['PATH_INFO']), casts it to
media type, and prepends it to env['HTTP_ACCEPT']. This allows dealing with path
information separately from format information, which are often different
concerns.

This is especially useful when dealing with routes as it allows a resource to
always point to the same action independently from the requested format.

===== Usage

require 'rack'
require 'rack/abstract_format'

use Rack::AbstractFormat
run app

The request:

  GET /path/resource.xml
  Accept: text/html

will become:

  GET /path/resource
  env['HTTP_ACCEPT'] #=> 'application/xml,text/html'