source 'https://rubygems.org' gemspec gem 'rake' rails = ENV['RAILS'] || 'master' if rails == 'master' arel = ENV['AREL'] || 'master' arel_opts = case arel when /\// # A path { path: arel } when /^v/ # A tagged version { git: 'git://github.com/rails/arel.git', tag: arel } else { git: 'git://github.com/rails/arel.git', branch: arel } end gem 'arel', arel_opts end case rails when /\// # A path gem 'activerecord', path: "#{rails}/activerecord" when /^v/ # A tagged version git 'git://github.com/rails/rails.git', tag: rails do gem 'activerecord' end else git 'git://github.com/rails/rails.git', branch: rails do gem 'activerecord' end end