15 files changed, 138 insertions, 73 deletions
diff --git a/guides/source/2_3_release_notes.md b/guides/source/2_3_release_notes.md
index 6976848e95..3f5a3c7ade 100644
--- a/guides/source/2_3_release_notes.md
+++ b/guides/source/2_3_release_notes.md
@@ -10,7 +10,7 @@ Rails 2.3 delivers a variety of new and improved features, including pervasive R
 Application Architecture
 ------------------------
 
-There are two major changes in the architecture of Rails applications: complete integration of the [Rack](http://rack.github.io/) modular web server interface, and renewed support for Rails Engines.
+There are two major changes in the architecture of Rails applications: complete integration of the [Rack](https://rack.github.io/) modular web server interface, and renewed support for Rails Engines.
 
 ### Rack Integration
 
diff --git a/guides/source/5_0_release_notes.md b/guides/source/5_0_release_notes.md
index 5f4be07351..6d53e1c2b4 100644
--- a/guides/source/5_0_release_notes.md
+++ b/guides/source/5_0_release_notes.md
@@ -55,7 +55,7 @@ information.
 ### API Applications
 
 Rails can now be used to create slimmed down API only applications.
-This is useful for creating and serving APIs similar to [Twitter](https://dev.twitter.com) or [GitHub](http://developer.github.com) API, 
+This is useful for creating and serving APIs similar to [Twitter](https://dev.twitter.com) or [GitHub](https://developer.github.com) API, 
 that can be used to serve public facing, as well as, for custom applications.
 
 You can generate a new api Rails app using:
@@ -74,11 +74,11 @@ This will do three main things:
   Controller modules that provide functionalities primarily used by browser
   applications.
 - Configure the generators to skip generating views, helpers and assets when
-  you generate a new resource. 
+  you generate a new resource.
 
-The application provides a base for APIs, 
+The application provides a base for APIs,
 that can then be [configured to pull in functionality](api_app.html) as suitable for the application's needs.  
- 
+
 See the [Using Rails for API-only Applications](api_app.html) guide for more
 information.
 
diff --git a/guides/source/active_record_validations.md b/guides/source/active_record_validations.md
index a086363cf1..e9157f3db1 100644
--- a/guides/source/active_record_validations.md
+++ b/guides/source/active_record_validations.md
@@ -892,7 +892,7 @@ Conditional Validation
 
 Sometimes it will make sense to validate an object only when a given predicate
 is satisfied. You can do that by using the `:if` and `:unless` options, which
-can take a symbol, a string, a `Proc` or an `Array`. You may use the `:if`
+can take a symbol, a `Proc` or an `Array`. You may use the `:if`
 option when you want to specify when the validation **should** happen. If you
 want to specify when the validation **should not** happen, then you may use the
 `:unless` option.
diff --git a/guides/source/api_app.md b/guides/source/api_app.md
index 64200ec242..5ec79de8a0 100644
--- a/guides/source/api_app.md
+++ b/guides/source/api_app.md
@@ -18,7 +18,7 @@ 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.
-For example, GitHub provides [an API](http://developer.github.com) that you
+For example, GitHub provides [an API](https://developer.github.com) that you
 can use from your own custom clients.
 
 With the advent of client-side frameworks, more developers are using Rails to
@@ -94,7 +94,7 @@ Handled at the Action Pack layer:
   means not having to spend time thinking about how to model your API in terms
   of HTTP.
 - URL Generation: The flip side of routing is URL generation. A good API based
-  on HTTP includes URLs (see [the GitHub Gist API](http://developer.github.com/v3/gists/)
+  on HTTP includes URLs (see [the GitHub Gist API](https://developer.github.com/v3/gists/)
   for an example).
 - Header and Redirection Responses: `head :no_content` and
   `redirect_to user_url(current_user)` come in handy. Sure, you could manually
diff --git a/guides/source/asset_pipeline.md b/guides/source/asset_pipeline.md
index 383e972f74..f148cef24f 100644
--- a/guides/source/asset_pipeline.md
+++ b/guides/source/asset_pipeline.md
@@ -1069,7 +1069,7 @@ Customizing the Pipeline
 ### CSS Compression
 
 One of the options for compressing CSS is YUI. The [YUI CSS
-compressor](http://yui.github.io/yuicompressor/css.html) provides
+compressor](https://yui.github.io/yuicompressor/css.html) provides
 minification.
 
 The following line enables YUI compression, and requires the `yui-compressor`
diff --git a/guides/source/autoloading_and_reloading_constants.md b/guides/source/autoloading_and_reloading_constants.md
index 05743ee4ce..c62194faf4 100644
--- a/guides/source/autoloading_and_reloading_constants.md
+++ b/guides/source/autoloading_and_reloading_constants.md
@@ -475,12 +475,21 @@ it is (edited):
 ```
 $ bin/rails r 'puts ActiveSupport::Dependencies.autoload_paths'
 .../app/assets
+.../app/channels
 .../app/controllers
+.../app/controllers/concerns
 .../app/helpers
+.../app/jobs
 .../app/mailers
 .../app/models
-.../app/controllers/concerns
 .../app/models/concerns
+.../activestorage/app/assets
+.../activestorage/app/controllers
+.../activestorage/app/javascript
+.../activestorage/app/jobs
+.../activestorage/app/models
+.../actioncable/app/assets
+.../actionview/app/assets
 .../test/mailers/previews
 ```
 
diff --git a/guides/source/command_line.md b/guides/source/command_line.md
index 8ae01286e4..2cd8e02a77 100644
--- a/guides/source/command_line.md
+++ b/guides/source/command_line.md
@@ -645,13 +645,16 @@ $ cat config/database.yml
 # Configure Using Gemfile
 # gem 'pg'
 #
-development:
+default: &default
   adapter: postgresql
   encoding: unicode
+  # For details on connection pooling, see Rails configuration guide
+  # http://guides.rubyonrails.org/configuring.html#database-pooling
+  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
+
+development:
+  <<: *default
   database: gitapp_development
-  pool: 5
-  username: gitapp
-  password:
 ...
 ...
 ```
diff --git a/guides/source/contributing_to_ruby_on_rails.md b/guides/source/contributing_to_ruby_on_rails.md
index 2f2962a3e6..7424818757 100644
--- a/guides/source/contributing_to_ruby_on_rails.md
+++ b/guides/source/contributing_to_ruby_on_rails.md
@@ -13,7 +13,7 @@ After reading this guide, you will know:
 * How to contribute to the Ruby on Rails documentation.
 * How to contribute to the Ruby on Rails code.
 
-Ruby on Rails is not "someone else's framework." Over the years, hundreds of people have contributed to Ruby on Rails ranging from a single character to massive architectural changes or significant documentation - all with the goal of making Ruby on Rails better for everyone. Even if you don't feel up to writing code or documentation yet, there are a variety of other ways that you can contribute, from reporting issues to testing patches.
+Ruby on Rails is not "someone else's framework." Over the years, thousands of people have contributed to Ruby on Rails ranging from a single character to massive architectural changes or significant documentation - all with the goal of making Ruby on Rails better for everyone. Even if you don't feel up to writing code or documentation yet, there are a variety of other ways that you can contribute, from reporting issues to testing patches.
 
 As mentioned in [Rails'
 README](https://github.com/rails/rails/blob/master/README.md), everyone interacting in Rails and its sub-projects' codebases, issue trackers, chat rooms, and mailing lists is expected to follow the Rails [code of conduct](http://rubyonrails.org/conduct/).
@@ -92,7 +92,7 @@ For starters, it helps just to verify bug reports. Can you reproduce the reporte
 
 If an issue is very vague, can you help narrow it down to something more specific? Maybe you can provide additional information to help reproduce a bug, or help by eliminating needless steps that aren't required to demonstrate the problem.
 
-If you find a bug report without a test, it's very useful to contribute a failing test. This is also a great way to get started exploring the source code: looking at the existing test files will teach you how to write more tests. New tests are best contributed in the form of a patch, as explained later on in the "Contributing to the Rails Code" section.
+If you find a bug report without a test, it's very useful to contribute a failing test. This is also a great way to get started exploring the source code: looking at the existing test files will teach you how to write more tests. New tests are best contributed in the form of a patch, as explained later on in the "[Contributing to the Rails Code](#contributing-to-the-rails-code)" section.
 
 Anything you can do to make bug reports more succinct or easier to reproduce helps folks trying to write code to fix those bugs - whether you end up writing the code yourself or not.
 
@@ -164,11 +164,11 @@ NOTE: The instructions are for Rails > 4. The Redcarpet Gem doesn't work with JR
 Translation efforts we know about (various versions):
 
 * **Italian**: [https://github.com/rixlabs/docrails](https://github.com/rixlabs/docrails)
-* **Spanish**: [http://wiki.github.com/gramos/docrails](http://wiki.github.com/gramos/docrails)
-* **Polish**: [https://github.com/apohllo/docrails/tree/master](https://github.com/apohllo/docrails/tree/master)
+* **Spanish**: [https://github.com/gramos/docrails/wiki](https://github.com/gramos/docrails/wiki)
+* **Polish**: [https://github.com/apohllo/docrails](https://github.com/apohllo/docrails)
 * **French** : [https://github.com/railsfrance/docrails](https://github.com/railsfrance/docrails)
 * **Czech** : [https://github.com/rubyonrails-cz/docrails/tree/czech](https://github.com/rubyonrails-cz/docrails/tree/czech)
-* **Turkish** : [https://github.com/ujk/docrails/tree/master](https://github.com/ujk/docrails/tree/master)
+* **Turkish** : [https://github.com/ujk/docrails](https://github.com/ujk/docrails)
 * **Korean** : [https://github.com/rorlakr/rails-guides](https://github.com/rorlakr/rails-guides)
 * **Simplified Chinese** : [https://github.com/ruby-china/guides](https://github.com/ruby-china/guides)
 * **Traditional Chinese** : [https://github.com/docrails-tw/guides](https://github.com/docrails-tw/guides)
@@ -184,7 +184,7 @@ To move on from submitting bugs to helping resolve existing issues or contributi
 
 #### The Easy Way
 
-The easiest and recommended way to get a development environment ready to hack is to use the [Rails development box](https://github.com/rails/rails-dev-box).
+The easiest and recommended way to get a development environment ready to hack is to use the [rails-dev-box](https://github.com/rails/rails-dev-box).
 
 #### The Hard Way
 
@@ -324,7 +324,7 @@ file.
 
 #### Testing Active Record
 
-First, create the databases you'll need. You can find a list of the required 
+First, create the databases you'll need. You can find a list of the required
 table names, usernames, and passwords in `activerecord/test/config.example.yml`.
 
 For MySQL and PostgreSQL, running the SQL statements `create database
@@ -480,7 +480,7 @@ Navigate to the Rails [GitHub repository](https://github.com/rails/rails) and pr
 Add the new remote to your local repository on your local machine:
 
 ```bash
-$ git remote add mine https://github.com:<your user name>/rails.git
+$ git remote add mine https://github.com/<your user name>/rails.git
 ```
 
 Push to your remote:
@@ -554,7 +554,7 @@ is the open source life.
 
 If it's been over a week, and you haven't heard anything, you might want to try
 and nudge things along. You can use the [rubyonrails-core mailing
-list](http://groups.google.com/group/rubyonrails-core/) for this. You can also
+list](https://groups.google.com/forum/#!forum/rubyonrails-core) for this. You can also
 leave another comment on the pull request.
 
 While you're waiting for feedback on your pull request, open up a few other
diff --git a/guides/source/debugging_rails_applications.md b/guides/source/debugging_rails_applications.md
index 7ea3646c30..99bc7c5fb5 100644
--- a/guides/source/debugging_rails_applications.md
+++ b/guides/source/debugging_rails_applications.md
@@ -186,21 +186,17 @@ end
 Here's an example of the log generated when this controller action is executed:
 
 ```
-Processing ArticlesController#create (for 127.0.0.1 at 2008-09-08 11:52:54) [POST]
-  Session ID: BAh7BzoMY3NyZl9pZCIlMDY5MWU1M2I1ZDRjODBlMzkyMWI1OTg2NWQyNzViZjYiCmZsYXNoSUM6J0FjdGl
-vbkNvbnRyb2xsZXI6OkZsYXNoOjpGbGFzaEhhc2h7AAY6CkB1c2VkewA=--b18cd92fba90eacf8137e5f6b3b06c4d724596a4
-  Parameters: {"commit"=>"Create", "article"=>{"title"=>"Debugging Rails",
- "body"=>"I'm learning how to print in logs!!!", "published"=>"0"},
- "authenticity_token"=>"2059c1286e93402e389127b1153204e0d1e275dd", "action"=>"create", "controller"=>"articles"}
-New article: {"updated_at"=>nil, "title"=>"Debugging Rails", "body"=>"I'm learning how to print in logs!!!",
- "published"=>false, "created_at"=>nil}
+Started POST "/articles" for 127.0.0.1 at 2017-08-20 20:53:10 +0900
+Processing by ArticlesController#create as HTML
+  Parameters: {"utf8"=>"✓", "authenticity_token"=>"xhuIbSBFytHCE1agHgvrlKnSVIOGD6jltW2tO+P6a/ACjQ3igjpV4OdbsZjIhC98QizWH9YdKokrqxBCJrtoqQ==", "article"=>{"title"=>"Debugging Rails", "body"=>"I'm learning how to print in logs!!!", "published"=>"0"}, "commit"=>"Create Article"}
+New article: {"id"=>nil, "title"=>"Debugging Rails", "body"=>"I'm learning how to print in logs!!!", "published"=>false, "created_at"=>nil, "updated_at"=>nil}
 Article should be valid: true
-  Article Create (0.000443)   INSERT INTO "articles" ("updated_at", "title", "body", "published",
- "created_at") VALUES('2008-09-08 14:52:54', 'Debugging Rails',
- 'I''m learning how to print in logs!!!', 'f', '2008-09-08 14:52:54')
+   (0.1ms)  BEGIN
+  SQL (0.4ms)  INSERT INTO "articles" ("title", "body", "published", "created_at", "updated_at") VALUES ($1, $2, $3, $4, $5) RETURNING "id"  [["title", "Debugging Rails"], ["body", "I'm learning how to print in logs!!!"], ["published", "f"], ["created_at", "2017-08-20 11:53:10.010435"], ["updated_at", "2017-08-20 11:53:10.010435"]]
+   (0.3ms)  COMMIT
 The article was saved and now the user is going to be redirected...
-Redirected to # Article:0x20af760>
-Completed in 0.01224 (81 reqs/sec) | DB: 0.00044 (3%) | 302 Found [http://localhost/articles]
+Redirected to http://localhost:3000/articles/1
+Completed 302 Found in 4ms (ActiveRecord: 0.8ms)
 ```
 
 Adding extra logging like this makes it easy to search for unexpected or unusual behavior in your logs. If you add extra logging, be sure to make sensible use of log levels to avoid filling your production logs with useless trivia.
diff --git a/guides/source/development_dependencies_install.md b/guides/source/development_dependencies_install.md
index c57efd6362..5a9729bb0f 100644
--- a/guides/source/development_dependencies_install.md
+++ b/guides/source/development_dependencies_install.md
@@ -21,24 +21,25 @@ The easiest and recommended way to get a development environment ready to hack i
 The Hard Way
 ------------
 
-In case you can't use the Rails development box, see section below, these are the steps to manually build a development box for Ruby on Rails core development.
+In case you can't use the Rails development box, see the steps below to manually
+build a development box for Ruby on Rails core development.
 
 ### Install Git
 
-Ruby on Rails uses Git for source code control. The [Git homepage](http://git-scm.com/) has installation instructions. There are a variety of resources on the net that will help you get familiar with Git:
+Ruby on Rails uses Git for source code control. The [Git homepage](https://git-scm.com/) has installation instructions. There are a variety of resources on the net that will help you get familiar with Git:
 
-* [Try Git course](http://try.github.io/) is an interactive course that will teach you the basics.
-* The [official Documentation](http://git-scm.com/documentation) is pretty comprehensive and also contains some videos with the basics of Git.
-* [Everyday Git](http://schacon.github.io/git/everyday.html) will teach you just enough about Git to get by.
-* [GitHub](http://help.github.com) offers links to a variety of Git resources.
-* [Pro Git](http://git-scm.com/book) is an entire book about Git with a Creative Commons license.
+* [Try Git course](https://try.github.io/) is an interactive course that will teach you the basics.
+* The [official Documentation](https://git-scm.com/documentation) is pretty comprehensive and also contains some videos with the basics of Git.
+* [Everyday Git](https://schacon.github.io/git/everyday.html) will teach you just enough about Git to get by.
+* [GitHub](https://help.github.com/) offers links to a variety of Git resources.
+* [Pro Git](https://git-scm.com/book) is an entire book about Git with a Creative Commons license.
 
 ### Clone the Ruby on Rails Repository
 
 Navigate to the folder where you want the Ruby on Rails source code (it will create its own `rails` subdirectory) and run:
 
 ```bash
-$ git clone git://github.com/rails/rails.git
+$ git clone https://github.com/rails/rails.git
 $ cd rails
 ```
 
@@ -62,7 +63,7 @@ $ sudo apt-get install sqlite3 libsqlite3-dev
 If you are on Fedora or CentOS, you're done with
 
 ```bash
-$ sudo yum install libsqlite3x libsqlite3x-devel 
+$ sudo yum install libsqlite3x libsqlite3x-devel
 ```
 
 If you are on Arch Linux, you will need to run:
@@ -96,7 +97,7 @@ This command will install all dependencies except the MySQL and PostgreSQL Ruby
 
 NOTE: If you would like to run the tests that use memcached, you need to ensure that you have it installed and running.
 
-You can use [Homebrew](http://brew.sh/) to install memcached on OS X:
+You can use [Homebrew](https://brew.sh/) to install memcached on macOS:
 
 ```bash
 $ brew install memcached
@@ -181,7 +182,7 @@ The Active Record test suite requires a custom config file: `activerecord/test/c
 To be able to run the suite for MySQL and PostgreSQL we need their gems. Install
 first the servers, their client libraries, and their development files.
 
-On OS X, you can run:
+On macOS, you can run:
 
 ```bash
 $ brew install mysql
@@ -190,7 +191,7 @@ $ brew install postgresql
 
 Follow the instructions given by Homebrew to start these.
 
-In Ubuntu just run:
+On Ubuntu, just run:
 
 ```bash
 $ sudo apt-get install mysql-server libmysqlclient-dev
@@ -260,34 +261,34 @@ with your development account, on Linux or BSD, you just have to run:
 $ sudo -u postgres createuser --superuser $USER
 ```
 
-and for OS X:
+and for macOS:
 
 ```bash
 $ createuser --superuser $USER
 ```
 
-Then you need to create the test databases with
+Then, you need to create the test databases with:
 
 ```bash
 $ cd activerecord
 $ bundle exec rake db:postgresql:build
 ```
 
-It is possible to build databases for both PostgreSQL and MySQL with
+It is possible to build databases for both PostgreSQL and MySQL with:
 
 ```bash
 $ cd activerecord
 $ bundle exec rake db:create
 ```
 
-You can cleanup the databases using
+You can cleanup the databases using:
 
 ```bash
 $ cd activerecord
 $ bundle exec rake db:drop
 ```
 
-NOTE: Using the rake task to create the test databases ensures they have the correct character set and collation.
+NOTE: Using the Rake task to create the test databases ensures they have the correct character set and collation.
 
 NOTE: You'll see the following warning (or localized warning) during activating HStore extension in PostgreSQL 9.1.x or earlier: "WARNING: => is deprecated as an operator".
 
@@ -299,11 +300,11 @@ Action Cable uses Redis as its default subscriptions adapter ([read more](action
 
 #### Install Redis From Source
 
-Redis' documentation discourage installations with package managers as those are usually outdated. Installing from source and bringing the server up is straight forward and well documented on [Redis' documentation](http://redis.io/download#installation).
+Redis' documentation discourage installations with package managers as those are usually outdated. Installing from source and bringing the server up is straight forward and well documented on [Redis' documentation](https://redis.io/download#installation).
 
 #### Install Redis From Package Manager
 
-On OS X, you can run:
+On macOS, you can run:
 
 ```bash
 $ brew install redis
@@ -311,7 +312,7 @@ $ brew install redis
 
 Follow the instructions given by Homebrew to start these.
 
-In Ubuntu just run:
+On Ubuntu, just run:
 
 ```bash
 $ sudo apt-get install redis-server
@@ -323,7 +324,7 @@ On Fedora or CentOS (requires EPEL enabled), just run:
 $ sudo yum install redis
 ```
 
-If you are running Arch Linux just run:
+If you are running Arch Linux, just run:
 
 ```bash
 $ sudo pacman -S redis
@@ -335,3 +336,43 @@ FreeBSD users will have to run the following:
 ```bash
 # portmaster databases/redis
 ```
+
+### Active Storage Setup
+
+When working on Active Storage, it is important to note that you need to
+install its JavaScript dependencies while working on that section of the
+codebase. In order to install these dependencies, it is necessary to
+have Yarn, a Node.js package manager, available on your system. A
+prerequisite for installing this package manager is that
+[Node.js](https://nodejs.org) is installed.
+
+
+On macOS, you can run:
+
+```bash
+brew install yarn
+```
+
+On Ubuntu, you can run:
+
+```bash
+curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
+echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
+
+sudo apt-get update && sudo apt-get install yarn
+```
+
+On Fedora or CentOS, just run:
+
+```bash
+sudo wget https://dl.yarnpkg.com/rpm/yarn.repo -O /etc/yum.repos.d/yarn.repo
+
+sudo yum install yarn
+```
+
+Finally, after installing Yarn, you will need to run the following
+command inside of the `activestorage` directory to install the dependencies:
+
+```bash
+yarn install
+```
diff --git a/guides/source/generators.md b/guides/source/generators.md
index 37af7a1310..b7b8262e4a 100644
--- a/guides/source/generators.md
+++ b/guides/source/generators.md
@@ -90,13 +90,15 @@ $ bin/rails generate generator initializer
       create  lib/generators/initializer/initializer_generator.rb
       create  lib/generators/initializer/USAGE
       create  lib/generators/initializer/templates
+      invoke  test_unit
+      create    test/lib/generators/initializer_generator_test.rb
 ```
 
 This is the generator just created:
 
 ```ruby
 class InitializerGenerator < Rails::Generators::NamedBase
-  source_root File.expand_path("templates", __dir__)
+  source_root File.expand_path('templates', __dir__)
 end
 ```
 
@@ -122,7 +124,7 @@ And now let's change the generator to copy this template when invoked:
 
 ```ruby
 class InitializerGenerator < Rails::Generators::NamedBase
-  source_root File.expand_path("templates", __dir__)
+  source_root File.expand_path('templates', __dir__)
 
   def copy_initializer_file
     copy_file "initializer.rb", "config/initializers/#{file_name}.rb"
@@ -241,6 +243,8 @@ $ bin/rails generate generator rails/my_helper
       create  lib/generators/rails/my_helper/my_helper_generator.rb
       create  lib/generators/rails/my_helper/USAGE
       create  lib/generators/rails/my_helper/templates
+      invoke  test_unit
+      create    test/lib/generators/rails/my_helper_generator_test.rb
 ```
 
 After that, we can delete both the `templates` directory and the `source_root`
@@ -510,13 +514,13 @@ Available options are:
 Any additional options passed to this method are put on the end of the line:
 
 ```ruby
-gem "devise", git: "git://github.com/plataformatec/devise", branch: "master"
+gem "devise", git: "https://github.com/plataformatec/devise.git", branch: "master"
 ```
 
 The above code will put the following line into `Gemfile`:
 
 ```ruby
-gem "devise", git: "git://github.com/plataformatec/devise", branch: "master"
+gem "devise", git: "https://github.com/plataformatec/devise.git", branch: "master"
 ```
 
 ### `gem_group`
diff --git a/guides/source/initialization.md b/guides/source/initialization.md
index ccad10f07d..0cfabe2a66 100644
--- a/guides/source/initialization.md
+++ b/guides/source/initialization.md
@@ -99,13 +99,15 @@ configure the load path for your Gemfile's dependencies.
 
 A standard Rails application depends on several gems, specifically:
 
+* actioncable
 * actionmailer
 * actionpack
 * actionview
+* activejob
 * activemodel
 * activerecord
+* activestorage
 * activesupport
-* activejob
 * arel
 * builder
 * bundler
@@ -131,7 +133,7 @@ Once `config/boot.rb` has finished, the next file that is required is
 `ARGV` array simply contains `server` which will be passed over:
 
 ```ruby
-require "rails/command"
+require_relative "command"
 
 aliases = {
   "g"  => "generate",
@@ -170,7 +172,7 @@ module Rails::Command
       namespace = namespace.to_s
       namespace = "help" if namespace.blank? || HELP_MAPPINGS.include?(namespace)
       namespace = "version" if %w( -v --version ).include? namespace
-    
+
       if command = find_by_namespace(namespace)
         command.perform(namespace, args, config)
       else
@@ -189,7 +191,7 @@ module Rails
     class ServerCommand < Base # :nodoc:
       def perform
         set_application_directory!
-  
+
         Rails::Server.new.tap do |server|
           # Require application after server sets environment to propagate
           # the --environment option.
@@ -311,7 +313,7 @@ def parse!(args)
   args, options = args.dup, {}
 
   option_parser(options).parse! args
-  
+
   options[:log_stdout] = options[:daemonize].blank? && (options[:environment] || Rails.env) == "development"
   options[:server]     = args.shift
   options
@@ -366,11 +368,11 @@ private
 
   def log_to_stdout
     wrapped_app # touch the app so the logger is set up
-  
+
     console = ActiveSupport::Logger.new(STDOUT)
     console.formatter = Rails.logger.formatter
     console.level = Rails.logger.level
-  
+
     unless ActiveSupport::Logger.logger_outputs_to?(Rails.logger, STDOUT)
       Rails.logger.extend(ActiveSupport::Logger.broadcast(console))
     end
@@ -537,6 +539,7 @@ require "rails"
   action_mailer/railtie
   active_job/railtie
   action_cable/engine
+  active_storage/engine
   rails/test_unit/railtie
   sprockets/railtie
 ).each do |railtie|
diff --git a/guides/source/rails_on_rack.md b/guides/source/rails_on_rack.md
index cef8450ee4..aa1476ecc0 100644
--- a/guides/source/rails_on_rack.md
+++ b/guides/source/rails_on_rack.md
@@ -125,7 +125,7 @@ use ActionDispatch::Flash
 use Rack::Head
 use Rack::ConditionalGet
 use Rack::ETag
-run MyApp.application.routes
+run MyApp::Application.routes
 ```
 
 The default middlewares shown here (and some others) are each summarized in the [Internal Middlewares](#internal-middleware-stack) section, below.
@@ -302,7 +302,7 @@ Resources
 
 ### Learning Rack
 
-* [Official Rack Website](http://rack.github.io)
+* [Official Rack Website](https://rack.github.io)
 * [Introducing Rack](http://chneukirchen.org/blog/archive/2007/02/introducing-rack.html)
 
 ### Understanding Middlewares
diff --git a/guides/source/security.md b/guides/source/security.md
index 56969c7aea..7736a4b224 100644
--- a/guides/source/security.md
+++ b/guides/source/security.md
@@ -1025,7 +1025,7 @@ Here is a list of common headers:
 * **X-Content-Type-Options:** _'nosniff' in Rails by default_ - stops the browser from guessing the MIME type of a file.
 * **X-Content-Security-Policy:** [A powerful mechanism for controlling which sites certain content types can be loaded from](http://w3c.github.io/webappsec/specs/content-security-policy/csp-specification.dev.html)
 * **Access-Control-Allow-Origin:** Used to control which sites are allowed to bypass same origin policies and send cross-origin requests.
-* **Strict-Transport-Security:** [Used to control if the browser is allowed to only access a site over a secure connection](http://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security)
+* **Strict-Transport-Security:** [Used to control if the browser is allowed to only access a site over a secure connection](https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security)
 
 Environmental Security
 ----------------------
@@ -1060,7 +1060,7 @@ Additional Resources
 
 The security landscape shifts and it is important to keep up to date, because missing a new vulnerability can be catastrophic. You can find additional resources about (Rails) security here:
 
-* Subscribe to the Rails security [mailing list](http://groups.google.com/group/rubyonrails-security).
-* [Brakeman - Rails Security Scanner](http://brakemanscanner.org/) - To perform static security analysis for Rails applications.
+* Subscribe to the Rails security [mailing list](https://groups.google.com/forum/#!forum/rubyonrails-security).
+* [Brakeman - Rails Security Scanner](https://brakemanscanner.org/) - To perform static security analysis for Rails applications.
 * [Keep up to date on the other application layers](http://secunia.com/) (they have a weekly newsletter, too).
 * A [good security blog](https://www.owasp.org) including the [Cross-Site scripting Cheat Sheet](https://www.owasp.org/index.php/DOM_based_XSS_Prevention_Cheat_Sheet).
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index 49a0584d51..651b86275a 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -397,6 +397,15 @@ When using Ruby 2.4, you can preserve the timezone of the receiver when calling
 
     ActiveSupport.to_time_preserves_timezone = false
 
+### Changes with JSON/JSONB serialization
+
+In Rails 5.0, how JSON/JSONB attributes are serialized and deserialized changed. Now, if
+you set a column equal to a `String`, Active Record will no longer turn that string
+into a `Hash`, and will instead only return the string. This is not limited to code
+interacting with models, but also affects `:default` column settings in `db/schema.rb`.
+It is recommended that you do not set columns equal to a `String`, but pass a `Hash`
+instead, which will be converted to and from a JSON string automatically.
+
 Upgrading from Rails 4.1 to Rails 4.2
 -------------------------------------