Use the proper shebang when using Ruby 1.9 or jruby or windows.

railties/lib/generators/base.rb

@@ -335,18 +335,21 @@ def self.get_options_from_invocations(group_options, base_options)
         # default value plus an instance helper method called shebang.
         #
         def self.add_shebang_option!
-          require 'rbconfig'
-          default = File.join(Config::CONFIG['bindir'], Config::CONFIG['ruby_install_name'])
-
-          class_option :ruby, :type => :string, :aliases => "-r", :default => default,
+          class_option :ruby, :type => :string, :aliases => "-r", :default => Thor::Util.ruby_command,
                               :desc => "Path to the Ruby binary of your choice", :banner => "PATH"
 
-          class_eval <<-METHOD, __FILE__, __LINE__
-            protected
-            def shebang
-              "#!\#{options[:ruby] || "/usr/bin/env ruby"}"
+          no_tasks {
+            define_method :shebang do
+              @shebang ||= begin
+                command = if options[:ruby] == Thor::Util.ruby_command
+                  "/usr/bin/env #{File.basename(Thor::Util.ruby_command)}"
+                else
+                  options[:ruby]
+                end
+                "#!#{command}"
+              end
             end
-          METHOD
+          }
         end
 
     end

railties/test/generators/app_generator_test.rb

@@ -109,6 +109,21 @@ def test_shebang_is_added_to_files
     ).each { |path| assert_file "script/#{path}", /#!foo\/bar\/baz/ }
   end
 
+  def test_shebang_when_is_the_same_as_default_use_env
+    run_generator ["--ruby", Thor::Util.ruby_command]
+
+    %w(
+      about
+      console
+      dbconsole
+      destroy
+      generate
+      plugin
+      runner
+      server
+    ).each { |path| assert_file "script/#{path}", /#!\/usr\/bin\/env/ }
+  end
+
   def test_rails_is_frozen
     generator(:freeze => true, :database => "sqlite3").expects(:run).with("rake rails:freeze:edge", false)
     silence(:stdout){ generator.invoke }