Reload rails on demand instead of doing it after every request

.gitignore

# Rails.root/.gitignore
config/watchr.notify

.watchr

# Rails.root/.watchr

bootstrap.rb

# rails/railties/lib/rails/application/bootstrap.rb
initializer :set_clear_dependencies_hook do
  unless config.cache_classes
    changed_at = Proc.new{ File.new(File.join(Rails.root, '.watchr')).mtime }
    last_change = changed_at.call

    ActionDispatch::Callbacks.before do
      change = changed_at.call                        
      if change > last_change
        Rails.logger.info("DETECTED CHANGES")
        last_change = change
        ActiveSupport::DescendantsTracker.clear
        ActiveSupport::Dependencies.clear
      end
    end
  end
end

development.rb

# Add to:
# Rails.root/config/environments/development.rb
#
# Faster code reloading:

if defined?(Rails::Server) # `rails s` only (not in `rails console`)
  fork do
    exec("watchr", "script/touch.watchr")
  end
end

Gemfile

# Rails.root/Gemfile

# Bundle faster Rails instead:
gem 'rails', :git => 'git://github.com/paneq/rails.git', :branch => '3-0-7-faster' # https://github.com/paneq/rails/commit/9d1b49b1d409d8320dd537a407f42d7af27172fc
gem 'watchr'

touch.watchr

# Rails.root/script/touch.watchr
require 'fileutils'
rails_root = File.expand_path('../..', __FILE__)
watchr_file = File.join(rails_root, '.watchr')
watch( 'app/(.*)\.rb' ) do |md|
  FileUtils.touch(watchr_file)
  begin
    `test -f ./config/watchr.notify && notify-send -u low "Changed: #{md}"` # Notify on Ubuntu
  rescue Errno::ENOENT
  end
end