12 files changed, 127 insertions, 54 deletions
diff --git a/guides/source/5_0_release_notes.md b/guides/source/5_0_release_notes.md
index d380ba8fce..dc631e5cb9 100644
--- a/guides/source/5_0_release_notes.md
+++ b/guides/source/5_0_release_notes.md
@@ -256,6 +256,12 @@ Please refer to the [Changelog][action-pack] for detailed changes.
 *   Rails will only generate "weak", instead of strong ETags.
     ([Pull Request](https://github.com/rails/rails/pull/17573))
 
+*   Controller actions without an explicit `render` call and with no
+    corresponding templates will render `head :no_content` implicitly
+    instead of raising an error.
+    (Pull Request [1](https://github.com/rails/rails/pull/19377),
+    [2](https://github.com/rails/rails/pull/23827))
+
 Action View
 -------------
 
@@ -294,6 +300,9 @@ Please refer to the [Changelog][action-view] for detailed changes.
     button on submit to prevent double submits.
     ([Pull Request](https://github.com/rails/rails/pull/21135))
 
+*   Downcase model name in form submit tags rather than humanize.
+    ([Pull Request](https://github.com/rails/rails/pull/22764))
+
 
 Action Mailer
 -------------
@@ -313,6 +322,9 @@ Please refer to the [Changelog][action-mailer] for detailed changes.
 *   Template lookup now respects default locale and I18n fallbacks.
     ([commit](https://github.com/rails/rails/commit/ecb1981b))
 
+*   Template can use fragment cache like Action View template.
+    ([Pull Request](https://github.com/rails/rails/pull/22825))
+
 *   Added `_mailer` suffix to mailers created via generator, following the same
     naming convention used in controllers and jobs.
     ([Pull Request](https://github.com/rails/rails/pull/18074))
@@ -324,6 +336,9 @@ Please refer to the [Changelog][action-mailer] for detailed changes.
     the mailer queue name.
     ([Pull Request](https://github.com/rails/rails/pull/18587))
 
+*   Added `config.action_mailer.perform_caching` configuration to determine whether your templates should perform caching or not.
+    ([Pull Request](https://github.com/rails/rails/pull/22825))
+
 
 Active Record
 -------------
diff --git a/guides/source/action_mailer_basics.md b/guides/source/action_mailer_basics.md
index 91ea4efb55..558c16f5b0 100644
--- a/guides/source/action_mailer_basics.md
+++ b/guides/source/action_mailer_basics.md
@@ -407,6 +407,22 @@ use the rendered text for the text part. The render command is the same one used
 inside of Action Controller, so you can use all the same options, such as
 `:text`, `:inline` etc.
 
+#### Caching mailer view
+
+You can do cache in mailer views like in application views using `cache` method.
+
+```
+<% cache do %>
+  <%= @company.name %>
+<% end %>
+```
+
+And in order to use this feature, you need to configure your application with this:
+
+```
+  config.action_mailer.perform_caching = true
+```
+
 ### Action Mailer Layouts
 
 Just like controller views, you can also have mailer layouts. The layout name
diff --git a/guides/source/action_view_overview.md b/guides/source/action_view_overview.md
index 5e6eae1071..29e0943741 100644
--- a/guides/source/action_view_overview.md
+++ b/guides/source/action_view_overview.md
@@ -599,7 +599,7 @@ This would add something like "Process data files (0.34523)" to the log, which y
 
 #### cache
 
-A method for caching fragments of a view rather than an entire action or page. This technique is useful for caching pieces like menus, lists of news topics, static HTML fragments, and so on. This method takes a block that contains the content you wish to cache. See `ActionController::Caching::Fragments` for more information.
+A method for caching fragments of a view rather than an entire action or page. This technique is useful for caching pieces like menus, lists of news topics, static HTML fragments, and so on. This method takes a block that contains the content you wish to cache. See `AbstractController::Caching::Fragments` for more information.
 
 ```erb
 <% cache do %>
diff --git a/guides/source/api_app.md b/guides/source/api_app.md
index 563214896a..8dba914923 100644
--- a/guides/source/api_app.md
+++ b/guides/source/api_app.md
@@ -13,8 +13,8 @@ In this guide you will learn:
 
 --------------------------------------------------------------------------------
 
-What is an API app?
--------------------
+What is an API Application?
+---------------------------
 
 Traditionally, when people said that they used Rails as an "API", they meant
 providing a programmatically accessible API alongside their web application.
@@ -28,15 +28,14 @@ applications.
 For example, Twitter uses its [public API](https://dev.twitter.com) in its web
 application, which is built as a static site that consumes JSON resources.
 
-Instead of using Rails to generate dynamic HTML that will communicate with the
-server through forms and links, many developers are treating their web application
-as just another client, delivered as static HTML, CSS and JavaScript  consuming
-a simple JSON API.
+Instead of using Rails to generate HTML that communicates with the server
+through forms and links, many developers are treating their web application as
+just an API client delivered as HTML with JavaScript that consumes a JSON API.
 
 This guide covers building a Rails application that serves JSON resources to an
-API client **or** a client-side framework.
+API client, including client-side frameworks.
 
-Why use Rails for JSON APIs?
+Why Use Rails for JSON APIs?
 ----------------------------
 
 The first question a lot of people have when thinking about building a JSON API
@@ -75,7 +74,7 @@ Handled at the middleware layer:
   URL-encoded String? No problem. Rails will decode the JSON for you and make
   it available in `params`. Want to use nested URL-encoded parameters? That
   works too.
-- Conditional GETs: Rails handles conditional `GET`, (`ETag` and `Last-Modified`),
+- Conditional GETs: Rails handles conditional `GET` (`ETag` and `Last-Modified`)
   processing request headers and returning the correct response headers and status
   code. All you need to do is use the
   [`stale?`](http://api.rubyonrails.org/classes/ActionController/ConditionalGet.html#method-i-stale-3F)
@@ -104,21 +103,21 @@ Handled at the Action Pack layer:
   add the response headers, but why?
 - Caching: Rails provides page, action and fragment caching. Fragment caching
   is especially helpful when building up a nested JSON object.
-- Basic, Digest and Token Authentication: Rails comes with out-of-the-box support
+- Basic, Digest, and Token Authentication: Rails comes with out-of-the-box support
   for three kinds of HTTP authentication.
-- Instrumentation: Rails has an instrumentation API that will trigger registered
+- Instrumentation: Rails has an instrumentation API that triggers registered
   handlers for a variety of events, such as action processing, sending a file or
   data, redirection, and database queries. The payload of each event comes with
   relevant information (for the action processing event, the payload includes
   the controller, action, parameters, request format, request method and the
   request's full path).
-- Generators: This may be passé for advanced Rails users, but it can be nice to
-  generate a resource and get your model, controller, test stubs, and routes
-  created for you in a single command.
+- Generators: It is often handy to generate a resource and get your model,
+  controller, test stubs, and routes created for you in a single command for
+  further tweaking. Same for migrations and others.
 - Plugins: Many third-party libraries come with support for Rails that reduce
   or eliminate the cost of setting up and gluing together the library and the
   web framework. This includes things like overriding default generators, adding
-  rake tasks, and honoring Rails choices (like the logger and cache back-end).
+  Rake tasks, and honoring Rails choices (like the logger and cache back-end).
 
 Of course, the Rails boot process also glues together all registered components.
 For example, the Rails boot process is what uses your `config/database.yml` file
@@ -167,14 +166,23 @@ class definition:
 config.api_only = true
 ```
 
-Optionally, in `config/environments/development.rb` add the following line
-to render error responses using the API format (JSON by default) when it
-is a local request:
+In `config/environments/development.rb`, set `config.debug_exception_response_format`
+to configure the format used in responses when errors occur in development mode.
+
+To render an HTML page with debugging information, use the value `:default`.
+
+```ruby
+config.debug_exception_response_format = :default
+```
+
+To render debugging information preserving the response format, use the value `:api`.
 
 ```ruby
 config.debug_exception_response_format = :api
 ```
 
+By default, `config.debug_exception_response_format` is set to `:api`.
+
 Finally, inside `app/controllers/application_controller.rb`, instead of:
 
 ```ruby
diff --git a/guides/source/asset_pipeline.md b/guides/source/asset_pipeline.md
index 5dd54bf8ad..b6c612794c 100644
--- a/guides/source/asset_pipeline.md
+++ b/guides/source/asset_pipeline.md
@@ -335,8 +335,8 @@ include the 'data-turbolinks-track' option which causes turbolinks to check if
 an asset has been updated and if so loads it into the page:
 
 ```erb
-<%= stylesheet_link_tag "application", media: "all", "data-turbolinks-track" => true %>
-<%= javascript_include_tag "application", "data-turbolinks-track" => true %>
+<%= stylesheet_link_tag "application", media: "all", "data-turbolinks-track" => "reload" %>
+<%= javascript_include_tag "application", "data-turbolinks-track" => "reload" %>
 ```
 
 In regular views you can access images in the `public/assets/images` directory
diff --git a/guides/source/caching_with_rails.md b/guides/source/caching_with_rails.md
index 3a1a1ccfe6..f26019c72e 100644
--- a/guides/source/caching_with_rails.md
+++ b/guides/source/caching_with_rails.md
@@ -521,6 +521,14 @@ class ProductsController < ApplicationController
 end
 ```
 
+### A note on weak ETags
+
+Etags generated by Rails are weak by default. Weak etags allow symantically equivalent responses to have the same etags, even if their bodies do not match exactly. This is useful when we don't want the page to be regenerated for minor changes in response body. If you absolutely need to generate a strong etag, it can be assigned to the header directly.
+
+```ruby
+  response.add_header "ETag", Digest::MD5.hexdigest(response.body)
+```
+
 References
 ----------
 
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index a5fb396f15..b83d25c683 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -98,13 +98,15 @@ application. Accepts a valid week day symbol (e.g. `:monday`).
 
 * `config.exceptions_app` sets the exceptions application invoked by the ShowException middleware when an exception happens. Defaults to `ActionDispatch::PublicExceptions.new(Rails.public_path)`.
 
+* `config.debug_exception_response_format` sets the format used in responses when errors occur in development mode.
+
 * `config.file_watcher` is the class used to detect file updates in the file system when `config.reload_classes_only_on_change` is true. Rails ships with `ActiveSupport::FileUpdateChecker`, the default, and `ActiveSupport::EventedFileUpdateChecker` (this one depends on the [listen](https://github.com/guard/listen) gem). Custom classes must conform to the `ActiveSupport::FileUpdateChecker` API.
 
 * `config.filter_parameters` used for filtering out the parameters that
 you don't want shown in the logs, such as passwords or credit card
 numbers. New applications filter out passwords by adding the following `config.filter_parameters+=[:password]` in `config/initializers/filter_parameter_logging.rb`.
 
-* `config.force_ssl` forces all requests to be served over HTTPS by using the `ActionDispatch::SSL` middleware. This can be configured by setting `config.ssl_options` - see the [ActionDispatch::SSL documentation](http://edgeapi.rubyonrails.org/classes/ActionDispatch/SSL.html) for details.
+* `config.force_ssl` forces all requests to be served over HTTPS by using the `ActionDispatch::SSL` middleware, and sets `config.action_mailer.default_url_options` to be `{ protocol: 'https' }`. This can be configured by setting `config.ssl_options` - see the [ActionDispatch::SSL documentation](http://edgeapi.rubyonrails.org/classes/ActionDispatch/SSL.html) for details.
 
 * `config.log_formatter` defines the formatter of the Rails logger. This option defaults to an instance of `ActiveSupport::Logger::SimpleFormatter` for all modes except production, where it defaults to `Logger::Formatter`.
 
@@ -531,6 +533,9 @@ There are a number of settings available on `config.action_mailer`:
 * `config.action_mailer.deliver_later_queue_name` specifies the queue name for
   mailers. By default this is `mailers`.
 
+* `config.action_mailer.perform_caching` specifies whether the mailer templates should perform fragment caching or not. By default this is false in all environments.
+
+
 ### Configuring Active Support
 
 There are a few configuration options available in Active Support:
@@ -610,6 +615,17 @@ There are a few configuration options available in Active Support:
 
 * `config.active_job.logger` accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then used to log information from Active Job. You can retrieve this logger by calling `logger` on either an Active Job class or an Active Job instance. Set to `nil` to disable logging.
 
+### Configuring Action Cable
+
+* `config.action_cable.url` accepts a string for the URL for where
+ you are hosting your Action Cable server. You would use this option
+if you are running Action Cable servers that are separated from your
+main application.
+* `config.action_cable.mount_path` accepts a string for where to mount Action
+  Cable, as apart of the main server process. Defaults to `/cable`.
+You can set this as nil to not mount Action Cable as apart of your
+normal Rails server.
+
 ### Configuring a Database
 
 Just about every Rails application will interact with a database. You can connect to the database by setting an environment variable `ENV['DATABASE_URL']` or by using a configuration file called `config/database.yml`.
diff --git a/guides/source/form_helpers.md b/guides/source/form_helpers.md
index 2a289dd33a..422bc647ef 100644
--- a/guides/source/form_helpers.md
+++ b/guides/source/form_helpers.md
@@ -317,7 +317,7 @@ The Article model is directly available to users of the application, so - follow
 resources :articles
 ```
 
-TIP: Declaring a resource has a number of side-affects. See [Rails Routing From the Outside In](routing.html#resource-routing-the-rails-default) for more information on setting up and using resources.
+TIP: Declaring a resource has a number of side effects. See [Rails Routing From the Outside In](routing.html#resource-routing-the-rails-default) for more information on setting up and using resources.
 
 When dealing with RESTful resources, calls to `form_for` can get significantly easier if you rely on **record identification**. In short, you can just pass the model instance and have Rails figure out model name and the rest:
 
diff --git a/guides/source/getting_started.md b/guides/source/getting_started.md
index 8eb3b6190f..4431512eda 100644
--- a/guides/source/getting_started.md
+++ b/guides/source/getting_started.md
@@ -298,26 +298,30 @@ Open the file `config/routes.rb` in your editor.
 Rails.application.routes.draw do
   get 'welcome/index'
 
-  # The priority is based upon order of creation:
-  # first created -> highest priority.
-  # See how all your routes lay out with "bin/rails routes".
-  #
-  # You can have the root of your site routed with "root"
-  # root 'welcome#index'
-  #
-  # ...
+  # For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html
+
+  # Serve websocket cable requests in-process
+  # mount ActionCable.server => '/cable'
+end
 ```
 
 This is your application's _routing file_ which holds entries in a special
 [DSL (domain-specific language)](http://en.wikipedia.org/wiki/Domain-specific_language)
 that tells Rails how to connect incoming requests to
-controllers and actions. This file contains many sample routes on commented
-lines, and one of them actually shows you how to connect the root of your site
-to a specific controller and action. Find the line beginning with `root` and
-uncomment it. It should look something like the following:
+controllers and actions.
+Edit this file by adding the line of code `root 'welcome#index'`.
+It should look something like the following:
 
 ```ruby
-root 'welcome#index'
+Rails.application.routes.draw do
+  get 'welcome/index'
+
+  # For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html
+
+  # Serve websocket cable requests in-process
+  # mount ActionCable.server => '/cable'
+  root 'welcome#index'
+end
 ```
 
 `root 'welcome#index'` tells Rails to map requests to the root of the
@@ -348,7 +352,7 @@ operations are referred to as _CRUD_ operations.
 
 Rails provides a `resources` method which can be used to declare a standard REST
 resource. You need to add the _article resource_ to the
-`config/routes.rb` as follows:
+`config/routes.rb` so the file will look as follows:
 
 ```ruby
 Rails.application.routes.draw do
@@ -625,7 +629,7 @@ end
 The `render` method here is taking a very simple hash with a key of `:plain` and
 value of `params[:article].inspect`. The `params` method is the object which
 represents the parameters (or fields) coming in from the form. The `params`
-method returns an `ActiveSupport::HashWithIndifferentAccess` object, which
+method returns an `ActionController::Parameters` object, which
 allows you to access the keys of the hash using either strings or symbols. In
 this situation, the only parameters that matter are the ones from the form.
 
@@ -635,7 +639,7 @@ If you re-submit the form one more time you'll now no longer get the missing
 template error. Instead, you'll see something that looks like the following:
 
 ```ruby
-{"title"=>"First article!", "text"=>"This is my first article."}
+<ActionController::Parameters {"title"=>"First Article!", "text"=>"This is my first article."} permitted: false>
 ```
 
 This action is now displaying the parameters for the article that are coming in
diff --git a/guides/source/rails_application_templates.md b/guides/source/rails_application_templates.md
index 5a46baff2d..3bb5d3c8a6 100644
--- a/guides/source/rails_application_templates.md
+++ b/guides/source/rails_application_templates.md
@@ -22,7 +22,7 @@ $ rails new blog -m ~/template.rb
 $ rails new blog -m http://example.com/template.rb
 ```
 
-You can use the rake task `rails:template` to apply templates to an existing Rails application. The location of the template needs to be passed in to an environment variable named LOCATION. Again, this can either be path to a file or a URL.
+You can use the task `rails:template` to apply templates to an existing Rails application. The location of the template needs to be passed in to an environment variable named LOCATION. Again, this can either be path to a file or a URL.
 
 ```bash
 $ bin/rails rails:template LOCATION=~/template.rb
@@ -38,7 +38,7 @@ The Rails templates API is easy to understand. Here's an example of a typical Ra
 # template.rb
 generate(:scaffold, "person name:string")
 route "root to: 'people#index'"
-rake("db:migrate")
+rails_command("db:migrate")
 
 after_bundle do
   git :init
@@ -175,18 +175,24 @@ Executes an arbitrary command. Just like the backticks. Let's say you want to re
 run "rm README.rdoc"
 ```
 
-### rake(command, options = {})
+### rails_command(command, options = {})
 
-Runs the supplied rake tasks in the Rails application. Let's say you want to migrate the database:
+Runs the supplied task in the Rails application. Let's say you want to migrate the database:
 
 ```ruby
-rake "db:migrate"
+rails_command "db:migrate"
 ```
 
-You can also run rake tasks with a different Rails environment:
+You can also run tasks with a different Rails environment:
 
 ```ruby
-rake "db:migrate", env: 'production'
+rails_command "db:migrate", env: 'production'
+```
+
+You can also run tasks as a super-user:
+
+```ruby
+rails_command "log:clear", sudo: true
 ```
 
 ### route(routing_code)
@@ -226,7 +232,7 @@ CODE
 These methods let you ask questions from templates and decide the flow based on the user's answer. Let's say you want to Freeze Rails only if the user wants to:
 
 ```ruby
-rake("rails:freeze:gems") if yes?("Freeze rails gems?")
+rails_command("rails:freeze:gems") if yes?("Freeze rails gems?")
 # no?(question) acts just the opposite.
 ```
 
diff --git a/guides/source/testing.md b/guides/source/testing.md
index 7a9a30f7ac..09eec7a64c 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -287,7 +287,7 @@ specify to make your test failure messages clearer.
 | `assert_not_in_delta( expected, actual, [delta], [msg] )`        | Ensures that the numbers `expected` and `actual` are not within `delta` of each other.|
 | `assert_throws( symbol, [msg] ) { block }`                       | Ensures that the given block throws the symbol.|
 | `assert_raises( exception1, exception2, ... ) { block }`         | Ensures that the given block raises one of the given exceptions.|
-| `assert_nothing_raised( exception1, exception2, ... ) { block }` | Ensures that the given block doesn't raise one of the given exceptions.|
+| `assert_nothing_raised { block }`                                | Ensures that the given block doesn't raise any exceptions.|
 | `assert_instance_of( class, obj, [msg] )`                        | Ensures that `obj` is an instance of `class`.|
 | `assert_not_instance_of( class, obj, [msg] )`                    | Ensures that `obj` is not an instance of `class`.|
 | `assert_kind_of( class, obj, [msg] )`                            | Ensures that `obj` is an instance of `class` or is descending from it.|
diff --git a/guides/source/working_with_javascript_in_rails.md b/guides/source/working_with_javascript_in_rails.md
index 26ff5da7a3..c58aee96db 100644
--- a/guides/source/working_with_javascript_in_rails.md
+++ b/guides/source/working_with_javascript_in_rails.md
@@ -350,8 +350,8 @@ $("<%= escape_javascript(render @user) %>").appendTo("#users");
 Turbolinks
 ----------
 
-Rails 4 ships with the [Turbolinks gem](https://github.com/turbolinks/turbolinks).
-This gem uses Ajax to speed up page rendering in most applications.
+Rails ships with the [Turbolinks library](https://github.com/turbolinks/turbolinks),
+which uses Ajax to speed up page rendering in most applications.
 
 ### How Turbolinks Works
 
@@ -364,14 +364,14 @@ will then use PushState to change the URL to the correct one, preserving
 refresh semantics and giving you pretty URLs.
 
 The only thing you have to do to enable Turbolinks is have it in your Gemfile,
-and put `//= require turbolinks` in your CoffeeScript manifest, which is usually
+and put `//= require turbolinks` in your JavaScript manifest, which is usually
 `app/assets/javascripts/application.js`.
 
-If you want to disable Turbolinks for certain links, add a `data-no-turbolink`
+If you want to disable Turbolinks for certain links, add a `data-turbolinks="false"`
 attribute to the tag:
 
 ```html
-<a href="..." data-no-turbolink>No turbolinks here</a>.
+<a href="..." data-turbolinks="false">No turbolinks here</a>.
 ```
 
 ### Page Change Events
@@ -389,7 +389,7 @@ event that this relies on will not be fired. If you have code that looks like
 this, you must change your code to do this instead:
 
 ```coffeescript
-$(document).on "page:change", ->
+$(document).on "turbolinks:load", ->
   alert "page has loaded!"
 ```