Add form_with_generates_remote_forms config.

Allows users to not have remote forms by default, since there's
more JS harness, e.g. bundling rails-ujs, otherwise.

Also don't skip creating defaults file anymore. Sprockets isn't the only new config.

actionview/lib/action_view/helpers/form_helper.rb

@@ -474,6 +474,8 @@ module ActionView
       end
       private :apply_form_for_options!
 
+      mattr_accessor(:form_with_generates_remote_forms) { true }
+
       # Creates a form tag based on mixing URLs, scopes, or models.
       #
       #   # Using just a URL:
@@ -1503,7 +1505,7 @@ module ActionView
       end
 
       private
-        def html_options_for_form_with(url_for_options = nil, model = nil, html: {}, local: false,
+        def html_options_for_form_with(url_for_options = nil, model = nil, html: {}, local: !form_with_generates_remote_forms,
           skip_enforcing_utf8: false, **options)
           html_options = options.slice(:id, :class, :multipart, :method, :data).merge(html)
           html_options[:method] ||= :patch if model.respond_to?(:persisted?) && model.persisted?

railties/lib/rails/generators/rails/app/app_generator.rb

@@ -403,9 +403,7 @@ module Rails
       end
 
       def delete_new_framework_defaults
-        # Sprockets owns the only new default for 5.1: if it's disabled,
-        # we don't want the file.
-        unless options[:update] && !options[:skip_sprockets]
+        unless options[:update]
           remove_file "config/initializers/new_framework_defaults_5_1.rb"
         end
       end

railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_5_1.rb.tt

@@ -5,6 +5,9 @@
 # Once upgraded flip defaults one by one to migrate to the new default.
 #
 # Read the Guide for Upgrading Ruby on Rails for more info on each option.
+
+# Make `form_with` generate non-remote forms.
+Rails.application.config.action_view.form_with_generates_remote_forms = false
 <%- unless options[:skip_sprockets] -%>
 
 # Unknown asset fallback will return the path passed in when the given

railties/test/generators/app_generator_test.rb

@@ -410,7 +410,6 @@ class AppGeneratorTest < Rails::Generators::TestCase
       assert_no_match(/config\.assets\.js_compressor = :uglifier/, content)
       assert_no_match(/config\.assets\.css_compressor = :sass/, content)
     end
-    assert_no_file "config/initializers/new_framework_defaults_5_1.rb"
   end
 
   def test_generator_if_skip_yarn_is_given