Shorten long line

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@2628 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

railties/environments/boot.rb

+unless defined?(RAILS_ROOT)
 require 'pathname'
-RAILS_ROOT = Pathname.new(File.join(File.dirname(__FILE__), '..')).cleanpath.to_s + '/' unless defined?(RAILS_ROOT)
+  root_path = Pathname.new(File.join(File.dirname(__FILE__), '..'))
+  RAILS_ROOT = root_path.cleanpath.to_s + '/'
+end
 
 if File.directory?("#{RAILS_ROOT}/vendor/rails")
   require "#{RAILS_ROOT}/vendor/rails/railties/lib/initializer"