9 files changed, 77 insertions, 105 deletions
diff --git a/guides/source/5_1_release_notes.md b/guides/source/5_1_release_notes.md
index d26d3d3b95..a5a7eb4b2e 100644
--- a/guides/source/5_1_release_notes.md
+++ b/guides/source/5_1_release_notes.md
@@ -399,7 +399,7 @@ Please refer to the [Changelog][action-view] for detailed changes.
 
 *   Change `datetime_field` and `datetime_field_tag` to generate `datetime-local`
     fields.
-    ([Pull Request](https://github.com/rails/rails/pull/28061))
+    ([Pull Request](https://github.com/rails/rails/pull/25469))
 
 *   New Builder-style syntax for HTML tags (`tag.div`, `tag.br`, etc.)
     ([Pull Request](https://github.com/rails/rails/pull/25543))
diff --git a/guides/source/action_mailer_basics.md b/guides/source/action_mailer_basics.md
index 041a427f7c..1acb993cad 100644
--- a/guides/source/action_mailer_basics.md
+++ b/guides/source/action_mailer_basics.md
@@ -839,13 +839,14 @@ Mailer Testing
 You can find detailed instructions on how to test your mailers in the
 [testing guide](testing.html#testing-your-mailers).
 
-Intercepting Emails
+Intercepting and Observing Emails
 -------------------
 
-There are situations where you need to edit an email before it's
-delivered. Fortunately Action Mailer provides hooks to intercept every
-email. You can register an interceptor to make modifications to mail messages
-right before they are handed to the delivery agents.
+Action Mailer provides hooks into the Mail observer and interceptor methods. These allow you to register classes that are called during the mail delivery life cycle of every email sent.
+
+### Intercepting Emails
+
+Interceptors allow you to make modifications to emails before they are handed off to the delivery agents. An interceptor class must implement the `:delivering_email(message)` method which will be called before the email is sent.
 
 ```ruby
 class SandboxEmailInterceptor
@@ -869,3 +870,21 @@ NOTE: The example above uses a custom environment called "staging" for a
 production like server but for testing purposes. You can read
 [Creating Rails environments](configuring.html#creating-rails-environments)
 for more information about custom Rails environments.
+
+### Observing Emails
+
+Observers give you access to the email message after it has been sent. An observer class must implement the `:delivered_email(message)` method, which will be called after the email is sent.
+
+```ruby
+class EmailDeliveryObserver
+  def self.delivered_email(message)
+    EmailDelivery.log(message)
+  end
+end
+```
+Like interceptors, you need to register observers with the Action Mailer framework. You can do this in an initializer file 
+`config/initializers/email_delivery_observer.rb`
+
+```ruby
+ActionMailer::Base.register_observer(EmailDeliveryObserver)
+```
diff --git a/guides/source/asset_pipeline.md b/guides/source/asset_pipeline.md
index 66cf9da33b..500e230ff9 100644
--- a/guides/source/asset_pipeline.md
+++ b/guides/source/asset_pipeline.md
@@ -233,11 +233,6 @@ code for JavaScript plugins and CSS frameworks. Keep in mind that third party
 code with references to other files also processed by the asset Pipeline (images,
 stylesheets, etc.), will need to be rewritten to use helpers like `asset_path`.
 
-WARNING: If you are upgrading from Rails 3, please take into account that assets
-under `lib/assets` or `vendor/assets` are available for inclusion via the
-application manifests but no longer part of the precompile array. See
-[Precompiling Assets](#precompiling-assets) for guidance.
-
 #### Search Paths
 
 When a file is referenced from a manifest or a helper, Sprockets searches the
@@ -1234,60 +1229,3 @@ it as a preprocessor for your mime type.
 Sprockets.register_preprocessor 'text/css', AddComment
 ```
 
-Upgrading from Old Versions of Rails
-------------------------------------
-
-There are a few issues when upgrading from Rails 3.0 or Rails 2.x. The first is
-moving the files from `public/` to the new locations. See [Asset
-Organization](#asset-organization) above for guidance on the correct locations
-for different file types.
-
-Next is updating the various environment files with the correct default
-options.
-
-In `application.rb`:
-
-```ruby
-# Version of your assets, change this if you want to expire all your assets
-config.assets.version = '1.0'
-
-# Change the path that assets are served from config.assets.prefix = "/assets"
-```
-
-In `development.rb`:
-
-```ruby
-# Expands the lines which load the assets
-config.assets.debug = true
-```
-
-And in `production.rb`:
-
-```ruby
-# Choose the compressors to use (if any)
-config.assets.js_compressor = :uglifier
-# config.assets.css_compressor = :yui
-
-# Don't fallback to assets pipeline if a precompiled asset is missed
-config.assets.compile = false
-
-# Generate digests for assets URLs.
-config.assets.digest = true
-
-# Precompile additional assets (application.js, application.css, and all
-# non-JS/CSS are already added)
-# config.assets.precompile += %w( admin.js admin.css )
-```
-
-Rails 4 and above no longer set default config values for Sprockets in `test.rb`, so
-`test.rb` now requires Sprockets configuration. The old defaults in the test
-environment are: `config.assets.compile = true`, `config.assets.compress = false`,
-`config.assets.debug = false` and `config.assets.digest = false`.
-
-The following should also be added to your `Gemfile`:
-
-```ruby
-gem 'sass-rails',   "~> 3.2.3"
-gem 'coffee-rails', "~> 3.2.1"
-gem 'uglifier'
-```
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md
index b0a905c754..78a1f47407 100644
--- a/guides/source/association_basics.md
+++ b/guides/source/association_basics.md
@@ -868,7 +868,7 @@ While Rails uses intelligent defaults that will work well in most situations, th
 
 ```ruby
 class Book < ApplicationRecord
-  belongs_to :author, dependent: :destroy,
+  belongs_to :author, touch: :books_updated_at,
     counter_cache: true
 end
 ```
@@ -1048,8 +1048,7 @@ There may be times when you wish to customize the query used by `belongs_to`. Su
 
 ```ruby
 class Book < ApplicationRecord
-  belongs_to :author, -> { where active: true },
-                        dependent: :destroy
+  belongs_to :author, -> { where active: true }
 end
 ```
 
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index 812565b207..61bb35cf93 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -200,8 +200,6 @@ The full set of methods that can be used in this block are as follows:
 * `helper` defines whether or not to generate helpers. Defaults to `true`.
 * `integration_tool` defines which integration tool to use to generate integration tests. Defaults to `:test_unit`.
 * `system_tests` defines which integration tool to use to generate system tests. Defaults to `:test_unit`.
-* `javascripts` turns on the hook for JavaScript files in generators. Used in Rails for when the `scaffold` generator is run. Defaults to `true`.
-* `javascript_engine` configures the engine to be used (for eg. coffee) when generating assets. Defaults to `:js`.
 * `orm` defines which orm to use. Defaults to `false` and will use Active Record by default.
 * `resource_controller` defines which generator to use for generating a controller when using `rails generate resource`. Defaults to `:controller`.
 * `resource_route` defines whether a resource route definition should be generated
diff --git a/guides/source/documents.yaml b/guides/source/documents.yaml
index 8f2312458d..551179c523 100644
--- a/guides/source/documents.yaml
+++ b/guides/source/documents.yaml
@@ -173,7 +173,7 @@
       description: This guide describes the considerations needed and tools available when working directly with concurrency in a Rails application.
       work_in_progress: true
 -
-  name: Contributing to Ruby on Rails
+  name: Contributions
   documents:
     -
       name: Contributing to Ruby on Rails
@@ -184,14 +184,14 @@
       url: api_documentation_guidelines.html
       description: This guide documents the Ruby on Rails API documentation guidelines.
     -
-      name: Ruby on Rails Guides Guidelines
+      name: Guides Guidelines
       url: ruby_on_rails_guides_guidelines.html
       description: This guide documents the Ruby on Rails guides guidelines.
 -
-  name: Maintenance Policy
+  name: Policies
   documents:
     -
-      name: Maintenance Policy for Ruby on Rails
+      name: Maintenance Policy
       url: maintenance_policy.html
       description: What versions of Ruby on Rails are currently supported, and when to expect new versions.
 -
@@ -202,51 +202,51 @@
       url: upgrading_ruby_on_rails.html
       description: This guide helps in upgrading applications to latest Ruby on Rails versions.
     -
-      name: Ruby on Rails 6.0 Release Notes
+      name: 6.0 Release Notes
       work_in_progress: true
       url: 6_0_release_notes.html
       description: Release notes for Rails 6.0.
     -
-      name: Ruby on Rails 5.2 Release Notes
+      name: 5.2 Release Notes
       url: 5_2_release_notes.html
       description: Release notes for Rails 5.2.
     -
-      name: Ruby on Rails 5.1 Release Notes
+      name: 5.1 Release Notes
       url: 5_1_release_notes.html
       description: Release notes for Rails 5.1.
     -
-      name: Ruby on Rails 5.0 Release Notes
+      name: 5.0 Release Notes
       url: 5_0_release_notes.html
       description: Release notes for Rails 5.0.
     -
-      name: Ruby on Rails 4.2 Release Notes
+      name: 4.2 Release Notes
       url: 4_2_release_notes.html
       description: Release notes for Rails 4.2.
     -
-      name: Ruby on Rails 4.1 Release Notes
+      name: 4.1 Release Notes
       url: 4_1_release_notes.html
       description: Release notes for Rails 4.1.
     -
-      name: Ruby on Rails 4.0 Release Notes
+      name: 4.0 Release Notes
       url: 4_0_release_notes.html
       description: Release notes for Rails 4.0.
     -
-      name: Ruby on Rails 3.2 Release Notes
+      name: 3.2 Release Notes
       url: 3_2_release_notes.html
       description: Release notes for Rails 3.2.
     -
-      name: Ruby on Rails 3.1 Release Notes
+      name: 3.1 Release Notes
       url: 3_1_release_notes.html
       description: Release notes for Rails 3.1.
     -
-      name: Ruby on Rails 3.0 Release Notes
+      name: 3.0 Release Notes
       url: 3_0_release_notes.html
       description: Release notes for Rails 3.0.
     -
-      name: Ruby on Rails 2.3 Release Notes
+      name: 2.3 Release Notes
       url: 2_3_release_notes.html
       description: Release notes for Rails 2.3.
     -
-      name: Ruby on Rails 2.2 Release Notes
+      name: 2.2 Release Notes
       url: 2_2_release_notes.html
       description: Release notes for Rails 2.2.
diff --git a/guides/source/generators.md b/guides/source/generators.md
index f028d14998..88ce4be8da 100644
--- a/guides/source/generators.md
+++ b/guides/source/generators.md
@@ -219,7 +219,7 @@ If we want to avoid generating the default `app/assets/stylesheets/scaffolds.scs
   end
 ```
 
-The next customization on the workflow will be to stop generating stylesheet, JavaScript, and test fixture files for scaffolds altogether. We can achieve that by changing our configuration to the following:
+The next customization on the workflow will be to stop generating stylesheet and test fixture files for scaffolds altogether. We can achieve that by changing our configuration to the following:
 
 ```ruby
 config.generators do |g|
@@ -227,7 +227,6 @@ config.generators do |g|
   g.template_engine :erb
   g.test_framework  :test_unit, fixture: false
   g.stylesheets     false
-  g.javascripts     false
 end
 ```
 
@@ -285,7 +284,6 @@ config.generators do |g|
   g.template_engine :erb
   g.test_framework  :test_unit, fixture: false
   g.stylesheets     false
-  g.javascripts     false
   g.helper          :my_helper
 end
 ```
@@ -350,7 +348,6 @@ config.generators do |g|
   g.template_engine :erb
   g.test_framework  :test_unit, fixture: false
   g.stylesheets     false
-  g.javascripts     false
 end
 ```
 
@@ -385,7 +382,6 @@ config.generators do |g|
   g.template_engine :erb
   g.test_framework  :shoulda, fixture: false
   g.stylesheets     false
-  g.javascripts     false
 
   # Add a fallback!
   g.fallbacks[:shoulda] = :test_unit
diff --git a/guides/source/i18n.md b/guides/source/i18n.md
index 78e5f27448..c61b6ad214 100644
--- a/guides/source/i18n.md
+++ b/guides/source/i18n.md
@@ -116,7 +116,7 @@ NOTE: The backend lazy-loads these translations when a translation is looked up
 You can change the default locale as well as configure the translations load paths in `config/application.rb` as follows:
 
 ```ruby
-  config.i18n.load_path += Dir[Rails.root.join('my', 'locales', '*.{rb,yml}').to_s]
+  config.i18n.load_path += Dir[Rails.root.join('my', 'locales', '*.{rb,yml}')]
   config.i18n.default_locale = :de
 ```
 
@@ -135,6 +135,8 @@ I18n.available_locales = [:en, :pt]
 I18n.default_locale = :pt
 ```
 
+Note that appending directly to `I18n.load_paths` instead of to the application's configured i18n will _not_ override translations from external gems.
+
 ### Managing the Locale across Requests
 
 The default locale is used for all translations unless `I18n.locale` is explicitly set.
@@ -662,6 +664,26 @@ I18n.t 'activerecord.errors.messages'
 # => {:inclusion=>"is not included in the list", :exclusion=> ... }
 ```
 
+If you want to perform interpolation on a bulk hash of translations, you need to pass `deep_interpolation: true` as a parameter. When you have the following dictionary:
+
+```yaml
+en:
+  welcome:
+    title: "Welcome!"
+    content: "Welcome to the %{app_name}"
+```
+
+then the nested interpolation will be ignored without the setting:
+
+```ruby
+I18n.t 'welcome', app_name: 'book store'
+# => {:title=>"Welcome!", :content=>"Welcome to the %{app_name}"}
+
+I18n.t 'welcome', deep_interpolation: true, app_name: 'book store'
+# => {:title=>"Welcome!", :content=>"Welcome to the book store"}
+```
+
+
 #### "Lazy" Lookup
 
 Rails implements a convenient way to look up the locale inside _views_. When you have the following dictionary:
@@ -1103,7 +1125,7 @@ For several reasons the Simple backend shipped with Active Support only does the
 
 That does not mean you're stuck with these limitations, though. The Ruby I18n gem makes it very easy to exchange the Simple backend implementation with something else that fits better for your needs, by passing a backend instance to the `I18n.backend=` setter.
 
-For example, you can replace the Simple backend with the the Chain backend to chain multiple backends together. This is useful when you want to use standard translations with a Simple backend but store custom application translations in a database or other backends.
+For example, you can replace the Simple backend with the Chain backend to chain multiple backends together. This is useful when you want to use standard translations with a Simple backend but store custom application translations in a database or other backends.
 
 With the Chain backend, you could use the Active Record backend and fall back to the (default) Simple backend:
 
diff --git a/guides/source/layout.html.erb b/guides/source/layout.html.erb
index dd9175e312..1f42d72756 100644
--- a/guides/source/layout.html.erb
+++ b/guides/source/layout.html.erb
@@ -45,16 +45,16 @@
           <a href="index.html" id="guidesMenu" class="guides-index-item nav-item">Guides Index</a>
           <div id="guides" class="clearfix" style="display: none;">
             <hr />
-            <% ['L', 'R'].each do |position| %>
-              <dl class="<%= position %>">
-              <% docs_for_menu(position).each do |section| %>
-                <dt><%= section['name'] %></dt>
-                <% finished_documents(section['documents']).each do |document| %>
-                <dd><a href="<%= document['url'] %>"><%= document['name'] %></a></dd>
-                <% end %>
+            <div class="guides-section-container">
+              <% documents_by_section.each do |section| %>
+                <div class="guides-section">
+                  <dt><%= section['name'] %></dt>
+                  <% finished_documents(section['documents']).each do |document| %>
+                  <dd><a href="<%= document['url'] %>"><%= document['name'] %></a></dd>
+                  <% end %>
+                </div>
               <% end %>
-              </dl>
-            <% end %>
+            </div>
           </div>
         </li>
         <li><a class="nav-item" href="contributing_to_ruby_on_rails.html">Contribute</a></li>