Detect rbenv and update the shebang

railties/lib/rails/generators/app_base.rb

@@ -261,7 +261,14 @@ def bundle_command(command)
       end
 
       def run_bundle
-        bundle_command('install --binstubs') unless options[:skip_gemfile] || options[:skip_bundle] || options[:pretend]
+        command = "install --binstubs"
+        command << " --shebang ruby-local-exec" if detect_ruby_local_exec
+
+        bundle_command(command) unless options[:skip_gemfile] || options[:skip_bundle] || options[:pretend]
+      end
+
+      def detect_ruby_local_exec
+        ENV["PATH"].split(":").find { |path| File.file?(File.join(path, "ruby-local-exec")) }
       end
 
       def empty_directory_with_keep_file(destination, config = {})

railties/test/generators/shared_generator_tests.rb

@@ -31,6 +31,16 @@ def test_generation_runs_bundle_install
     quietly { generator.invoke_all }
   end
 
+  def test_generation_runs_bundle_install_with_shebang_if_needed
+    original_path = ENV["PATH"]
+    ENV["PATH"] = ENV["PATH"] + ":" + File.expand_path("../../fixtures/path", __FILE__)
+
+    generator([destination_root]).expects(:bundle_command).with('install --binstubs --shebang ruby-local-exec').once
+    quietly { generator.invoke_all }
+  ensure
+    ENV["PATH"] = original_path
+  end
+
   def test_plugin_new_generate_pretend
     run_generator ["testapp", "--pretend"]
     default_files.each{ |path| assert_no_file File.join("testapp",path) }