refactor ruby version into it's own class

lib/bundler.rb

@@ -27,6 +27,7 @@ module Bundler
   autoload :MatchPlatform,         'bundler/match_platform'
   autoload :RemoteSpecification,   'bundler/remote_specification'
   autoload :Resolver,              'bundler/resolver'
+  autoload :RubyVersion,           'bundler/ruby_version'
   autoload :Runtime,               'bundler/runtime'
   autoload :Settings,              'bundler/settings'
   autoload :SharedHelpers,         'bundler/shared_helpers'

lib/bundler/dsl.rb

@@ -174,10 +174,8 @@ def ruby_version(ruby_version, options = {})
       raise GemfileError, "Please define :engine_version" if options[:engine] && options[:engine_version].nil?
       raise GemfileError, "Please define :engine" if options[:engine_version] && options[:engine].nil?
 
-      engine         = options[:engine] || "ruby"
       raise GemfileError, "ruby_version must match the :engine_version for MRI" if options[:engine] == "ruby" && options[:engine_version] && ruby_version != options[:engine_version]
-      engine_version = engine == "ruby" ? ruby_version : options[:engine_version]
-      @ruby_version  = "ruby #{ruby_version} (#{engine} #{engine_version})"
+      @ruby_version = RubyVersion.new(ruby_version, options[:engine], options[:engine_version])
     end
 
     def method_missing(name, *args)

lib/bundler/ruby_version.rb

@@ -0,0 +1,15 @@
+module Bundler
+  class RubyVersion
+    attr_reader :version, :engine, :engine_version
+
+    def initialize(version, engine, engine_version)
+      @version        = version
+      @engine         = engine || "ruby"
+      @engine_version = @engine == "ruby" ? version : engine_version
+    end
+
+    def to_s
+      "ruby #{@version} (#{@engine} #{@engine_version})"
+    end
+  end
+end