Mustache support for Middleman

middleman_mustache.rb

require 'tilt-mustache'

# Mustache Renderer
module Middleman::Renderers::Mustache
  class << self
    def registered(app)
      # Mustache is not included in the default gems,
      # but we'll support it if available.
      begin
        
        # Require Gem
        require "mustache"
        
        # After config, setup mustache partial paths
        app.after_configuration do          
          Mustache.template_path = source_dir

          # Convert data object into a hash for mustache
          provides_metadata %r{\.mustache$} do |path|
            { :locals => { :data => data.to_h } }
          end
        end
      rescue LoadError
      end
    end
    
    alias :included :registered
  end
end
Middleman::Base.register Middleman::Renderers::Mustache

Why is there the explicit call to register? With the current build, I get an error saying Base is not in scope.

Also, am I correct in thinking this passes the data through only for files that end in .mustache (e.g. not .ms)? I didn't see where provides_metadata was located.