How to install Rails 4.0-beta from scratch (on a non-dev machine) cf. http://www.zlu.me/blog/2012/10/29/install-and-create-rails-4-dot-0-app/

Gemfile

source 'https://rubygems.org'

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', github: 'rails/rails'
group :assets do
  gem 'uglifier', '>= 1.0.3'
end
gem 'journey', github: 'rails/journey'
gem 'activerecord-deprecated_finders', github: 'rails/activerecord-deprecated_finders'

rails4beta.sh

#!/bin/bash

bundle install
`bundle show rails`/railties/bin/rails new appname
bundle install