16 files changed, 125 insertions, 69 deletions
diff --git a/guides/source/4_0_release_notes.md b/guides/source/4_0_release_notes.md
index bbc0efa3ea..9feaff098a 100644
--- a/guides/source/4_0_release_notes.md
+++ b/guides/source/4_0_release_notes.md
@@ -59,25 +59,25 @@ Major Features
 
 ### Upgrade
 
- * **Ruby 1.9.3** ([commit](https://github.com/rails/rails/commit/a0380e808d3dbd2462df17f5d3b7fcd8bd812496)) - Ruby 2.0 preferred; 1.9.3+ required
- * **[New deprecation policy](http://www.youtube.com/watch?v=z6YgD6tVPQs)** - Deprecated features are warnings in Rails 4.0 and will be removed in Rails 4.1.
- * **ActionPack page and action caching** ([commit](https://github.com/rails/rails/commit/b0a7068564f0c95e7ef28fc39d0335ed17d93e90)) - Page and action caching are extracted to a separate gem. Page and action caching requires too much manual intervention (manually expiring caches when the underlying model objects are updated). Instead, use Russian doll caching.
- * **ActiveRecord observers** ([commit](https://github.com/rails/rails/commit/ccecab3ba950a288b61a516bf9b6962e384aae0b)) - Observers are extracted to a separate gem. Observers are only needed for page and action caching, and can lead to spaghetti code.
- * **ActiveRecord session store** ([commit](https://github.com/rails/rails/commit/0ffe19056c8e8b2f9ae9d487b896cad2ce9387ad)) - The ActiveRecord session store is extracted to a separate gem. Storing sessions in SQL is costly. Instead, use cookie sessions, memcache sessions, or a custom session store.
- * **ActiveModel mass assignment protection** ([commit](https://github.com/rails/rails/commit/f8c9a4d3e88181cee644f91e1342bfe896ca64c6)) - Rails 3 mass assignment protection is deprecated. Instead, use strong parameters.
- * **ActiveResource** ([commit](https://github.com/rails/rails/commit/f1637bf2bb00490203503fbd943b73406e043d1d)) - ActiveResource is extracted to a separate gem. ActiveResource was not widely used.
- * **vendor/plugins removed** ([commit](https://github.com/rails/rails/commit/853de2bd9ac572735fa6cf59fcf827e485a231c3)) - Use a Gemfile to manage installed gems.
+* **Ruby 1.9.3** ([commit](https://github.com/rails/rails/commit/a0380e808d3dbd2462df17f5d3b7fcd8bd812496)) - Ruby 2.0 preferred; 1.9.3+ required
+* **[New deprecation policy](http://www.youtube.com/watch?v=z6YgD6tVPQs)** - Deprecated features are warnings in Rails 4.0 and will be removed in Rails 4.1.
+* **ActionPack page and action caching** ([commit](https://github.com/rails/rails/commit/b0a7068564f0c95e7ef28fc39d0335ed17d93e90)) - Page and action caching are extracted to a separate gem. Page and action caching requires too much manual intervention (manually expiring caches when the underlying model objects are updated). Instead, use Russian doll caching.
+* **ActiveRecord observers** ([commit](https://github.com/rails/rails/commit/ccecab3ba950a288b61a516bf9b6962e384aae0b)) - Observers are extracted to a separate gem. Observers are only needed for page and action caching, and can lead to spaghetti code.
+* **ActiveRecord session store** ([commit](https://github.com/rails/rails/commit/0ffe19056c8e8b2f9ae9d487b896cad2ce9387ad)) - The ActiveRecord session store is extracted to a separate gem. Storing sessions in SQL is costly. Instead, use cookie sessions, memcache sessions, or a custom session store.
+* **ActiveModel mass assignment protection** ([commit](https://github.com/rails/rails/commit/f8c9a4d3e88181cee644f91e1342bfe896ca64c6)) - Rails 3 mass assignment protection is deprecated. Instead, use strong parameters.
+* **ActiveResource** ([commit](https://github.com/rails/rails/commit/f1637bf2bb00490203503fbd943b73406e043d1d)) - ActiveResource is extracted to a separate gem. ActiveResource was not widely used.
+* **vendor/plugins removed** ([commit](https://github.com/rails/rails/commit/853de2bd9ac572735fa6cf59fcf827e485a231c3)) - Use a Gemfile to manage installed gems.
 
 ### ActionPack
 
- * **Strong parameters** ([commit](https://github.com/rails/rails/commit/a8f6d5c6450a7fe058348a7f10a908352bb6c7fc)) - Only allow whitelisted parameters to update model objects (`params.permit(:title, :text)`).
- * **Routing concerns** ([commit](https://github.com/rails/rails/commit/0dd24728a088fcb4ae616bb5d62734aca5276b1b)) - In the routing DSL, factor out common subroutes (`comments` from `/posts/1/comments` and `/videos/1/comments`).
- * **ActionController::Live** ([commit](https://github.com/rails/rails/commit/af0a9f9eefaee3a8120cfd8d05cbc431af376da3)) - Stream JSON with `response.stream`.
- * **Declarative ETags** ([commit](https://github.com/rails/rails/commit/ed5c938fa36995f06d4917d9543ba78ed506bb8d)) - Add controller-level etag additions that will be part of the action etag computation.
- * **[Russian doll caching](http://37signals.com/svn/posts/3113-how-key-based-cache-expiration-works)** ([commit](https://github.com/rails/rails/commit/4154bf012d2bec2aae79e4a49aa94a70d3e91d49)) - Cache nested fragments of views. Each fragment expires based on a set of dependencies (a cache key). The cache key is usually a template version number and a model object.
- * **Turbolinks** ([commit](https://github.com/rails/rails/commit/e35d8b18d0649c0ecc58f6b73df6b3c8d0c6bb74)) - Serve only one initial HTML page. When the user navigates to another page, use pushState to update the URL and use AJAX to update the title and body.
- * **Decouple ActionView from ActionController** ([commit](https://github.com/rails/rails/commit/78b0934dd1bb84e8f093fb8ef95ca99b297b51cd)) - ActionView was decoupled from ActionPack and will be moved to a separated gem in Rails 4.1.
- * **Do not depend on ActiveModel** ([commit](https://github.com/rails/rails/commit/166dbaa7526a96fdf046f093f25b0a134b277a68)) - ActionPack no longer depends on ActiveModel.
+* **Strong parameters** ([commit](https://github.com/rails/rails/commit/a8f6d5c6450a7fe058348a7f10a908352bb6c7fc)) - Only allow whitelisted parameters to update model objects (`params.permit(:title, :text)`).
+* **Routing concerns** ([commit](https://github.com/rails/rails/commit/0dd24728a088fcb4ae616bb5d62734aca5276b1b)) - In the routing DSL, factor out common subroutes (`comments` from `/posts/1/comments` and `/videos/1/comments`).
+* **ActionController::Live** ([commit](https://github.com/rails/rails/commit/af0a9f9eefaee3a8120cfd8d05cbc431af376da3)) - Stream JSON with `response.stream`.
+* **Declarative ETags** ([commit](https://github.com/rails/rails/commit/ed5c938fa36995f06d4917d9543ba78ed506bb8d)) - Add controller-level etag additions that will be part of the action etag computation.
+* **[Russian doll caching](http://37signals.com/svn/posts/3113-how-key-based-cache-expiration-works)** ([commit](https://github.com/rails/rails/commit/4154bf012d2bec2aae79e4a49aa94a70d3e91d49)) - Cache nested fragments of views. Each fragment expires based on a set of dependencies (a cache key). The cache key is usually a template version number and a model object.
+* **Turbolinks** ([commit](https://github.com/rails/rails/commit/e35d8b18d0649c0ecc58f6b73df6b3c8d0c6bb74)) - Serve only one initial HTML page. When the user navigates to another page, use pushState to update the URL and use AJAX to update the title and body.
+* **Decouple ActionView from ActionController** ([commit](https://github.com/rails/rails/commit/78b0934dd1bb84e8f093fb8ef95ca99b297b51cd)) - ActionView was decoupled from ActionPack and will be moved to a separated gem in Rails 4.1.
+* **Do not depend on ActiveModel** ([commit](https://github.com/rails/rails/commit/166dbaa7526a96fdf046f093f25b0a134b277a68)) - ActionPack no longer depends on ActiveModel.
 
 ### General
 
@@ -95,9 +95,9 @@ NOTE: Check that the gems you are using are threadsafe.
 
 ### Security
 
- * **match do not catch all** ([commit](https://github.com/rails/rails/commit/90d2802b71a6e89aedfe40564a37bd35f777e541)) - In the routing DSL, match requires the HTTP verb or verbs to be specified.
- * **html entities escaped by default** ([commit](https://github.com/rails/rails/commit/5f189f41258b83d49012ec5a0678d827327e7543)) - Strings rendered in erb are escaped unless wrapped with `raw` or `html_safe` is called.
- * **New security headers** ([commit](https://github.com/rails/rails/commit/6794e92b204572d75a07bd6413bdae6ae22d5a82)) - Rails sends the following headers with every HTTP request: `X-Frame-Options` (prevents clickjacking by forbidding the browser from embedding the page in a frame), `X-XSS-Protection` (asks the browser to halt script injection) and `X-Content-Type-Options` (prevents the browser from opening a jpeg as an exe).
+* **match do not catch all** ([commit](https://github.com/rails/rails/commit/90d2802b71a6e89aedfe40564a37bd35f777e541)) - In the routing DSL, match requires the HTTP verb or verbs to be specified.
+* **html entities escaped by default** ([commit](https://github.com/rails/rails/commit/5f189f41258b83d49012ec5a0678d827327e7543)) - Strings rendered in erb are escaped unless wrapped with `raw` or `html_safe` is called.
+* **New security headers** ([commit](https://github.com/rails/rails/commit/6794e92b204572d75a07bd6413bdae6ae22d5a82)) - Rails sends the following headers with every HTTP request: `X-Frame-Options` (prevents clickjacking by forbidding the browser from embedding the page in a frame), `X-XSS-Protection` (asks the browser to halt script injection) and `X-Content-Type-Options` (prevents the browser from opening a jpeg as an exe).
 
 Extraction of features to gems
 ---------------------------
diff --git a/guides/source/4_2_release_notes.md b/guides/source/4_2_release_notes.md
index 366d9d26b4..684bd286bc 100644
--- a/guides/source/4_2_release_notes.md
+++ b/guides/source/4_2_release_notes.md
@@ -257,7 +257,7 @@ application is using any of these spellings, you will need to update them:
 *   Values in attribute selectors may need to be quoted if they contain
     non-alphanumeric characters.
 
-    ```
+    ```ruby
     # before
     a[href=/]
     a[href$=/]
@@ -272,7 +272,7 @@ application is using any of these spellings, you will need to update them:
 
     For example:
 
-    ``` ruby
+    ```ruby
     # content: <div><i><p></i></div>
 
     # before:
@@ -290,7 +290,7 @@ application is using any of these spellings, you will need to update them:
     used to be raw (e.g. `AT&amp;T`), and now is evaluated
     (e.g. `AT&T`).
 
-    ``` ruby
+    ```ruby
     # content: <p>AT&amp;T</p>
 
     # before:
@@ -302,6 +302,30 @@ application is using any of these spellings, you will need to update them:
     assert_select('p', 'AT&amp;T')  # => false
     ```
 
+Furthermore substitutions have changed syntax.
+
+Now you have to use a `:match` CSS-like selector:
+
+```ruby
+assert_select ":match('id', ?)", 'comment_1'
+```
+
+Additionally Regexp substitutions look different when the assertion fails.
+Notice how `/hello/` here:
+
+```ruby
+assert_select(":match('id', ?)", /hello/)
+```
+
+becomes `"(?-mix:hello)"`:
+
+```
+Expected at least 1 element matching "div:match('id', "(?-mix:hello)")", found 0..
+Expected 0 to be >= 1.
+```
+
+See the [Rails Dom Testing](https://github.com/rails/rails-dom-testing/tree/8798b9349fb9540ad8cb9a0ce6cb88d1384a210b) documentation for more on `assert_select`.
+
 
 Railties
 --------
diff --git a/guides/source/action_view_overview.md b/guides/source/action_view_overview.md
index 8f6676dc65..71f3f8882c 100644
--- a/guides/source/action_view_overview.md
+++ b/guides/source/action_view_overview.md
@@ -182,7 +182,7 @@ One way to use partials is to treat them as the equivalent of subroutines; a way
 
 <p>Here are a few of our fine products:</p>
 <% @products.each do |product| %>
-  <%= render partial: "product", locals: {product: product} %>
+  <%= render partial: "product", locals: { product: product } %>
 <% end %>
 
 <%= render "shared/footer" %>
@@ -197,7 +197,7 @@ these are the only options you want to pass, you can skip using these options.
 For example, instead of:
 
 ```erb
-<%= render partial: "product", locals: {product: @product} %>
+<%= render partial: "product", locals: { product: @product } %>
 ```
 
 You can also do:
@@ -217,7 +217,7 @@ By default `ActionView::Partials::PartialRenderer` has its object in a local var
 within product we'll get `@product` in the local variable `product`, as if we had written:
 
 ```erb
-<%= render partial: "product", locals: {product: @product} %>
+<%= render partial: "product", locals: { product: @product } %>
 ```
 
 With the `as` option we can specify a different name for the local variable. For example, if we wanted it to be `item` instead of `product` we would do:
@@ -231,7 +231,7 @@ The `object` option can be used to directly specify which object is rendered int
 For example, instead of:
 
 ```erb
-<%= render partial: "product", locals: {product: @item} %>
+<%= render partial: "product", locals: { product: @item } %>
 ```
 
 we would do:
@@ -304,7 +304,7 @@ In the `show` template, we'll render the `_article` partial wrapped in the `box`
 **articles/show.html.erb**
 
 ```erb
-<%= render partial: 'article', layout: 'box', locals: {article: @article} %>
+<%= render partial: 'article', layout: 'box', locals: { article: @article } %>
 ```
 
 The `box` layout simply wraps the `_article` partial in a `div`:
@@ -344,7 +344,7 @@ You can also render a block of code within a partial layout instead of calling `
 **articles/show.html.erb**
 
 ```html+erb
-<% render(layout: 'box', locals: {article: @article}) do %>
+<% render(layout: 'box', locals: { article: @article }) do %>
   <%= div_for(article) do %>
     <p><%= article.body %></p>
   <% end %>
@@ -407,7 +407,7 @@ stylesheet_link_tag :monkey # =>
 Returns a link tag that browsers and feed readers can use to auto-detect an RSS or Atom feed.
 
 ```ruby
-auto_discovery_link_tag(:rss, "http://www.example.com/feed.rss", {title: "RSS Feed"}) # =>
+auto_discovery_link_tag(:rss, "http://www.example.com/feed.rss", { title: "RSS Feed" }) # =>
   <link rel="alternate" type="application/rss+xml" title="RSS Feed" href="http://www.example.com/feed" />
 ```
 
@@ -789,7 +789,7 @@ time_select("order", "submitted")
 Returns a `pre` tag that has object dumped by YAML. This creates a very readable way to inspect an object.
 
 ```ruby
-my_hash = {'first' => 1, 'second' => 'two', 'third' => [1,2,3]}
+my_hash = { 'first' => 1, 'second' => 'two', 'third' => [1,2,3] }
 debug(my_hash)
 ```
 
@@ -814,7 +814,7 @@ The core method of this helper, form_for, gives you the ability to create a form
 
 ```html+erb
 # Note: a @person variable will have been created in the controller (e.g. @person = Person.new)
-<%= form_for @person, url: {action: "create"} do |f| %>
+<%= form_for @person, url: { action: "create" } do |f| %>
   <%= f.text_field :first_name %>
   <%= f.text_field :last_name %>
   <%= submit_tag 'Create' %>
@@ -834,7 +834,7 @@ The HTML generated for this would be:
 The params object created when this form is submitted would look like:
 
 ```ruby
-{"action" => "create", "controller" => "people", "person" => {"first_name" => "William", "last_name" => "Smith"}}
+{ "action" => "create", "controller" => "people", "person" => { "first_name" => "William", "last_name" => "Smith" } }
 ```
 
 The params hash has a nested person value, which can therefore be accessed with params[:person] in the controller.
@@ -855,7 +855,7 @@ check_box("article", "validated")
 Creates a scope around a specific model object like form_for, but doesn't create the form tags themselves. This makes fields_for suitable for specifying additional model objects in the same form:
 
 ```html+erb
-<%= form_for @person, url: {action: "update"} do |person_form| %>
+<%= form_for @person, url: { action: "update" } do |person_form| %>
   First name: <%= person_form.text_field :first_name %>
   Last name : <%= person_form.text_field :last_name %>
 
@@ -990,7 +990,7 @@ end
 Sample usage (selecting the associated Author for an instance of Article, `@article`):
 
 ```ruby
-collection_select(:article, :author_id, Author.all, :id, :name_with_initial, {prompt: true})
+collection_select(:article, :author_id, Author.all, :id, :name_with_initial, { prompt: true })
 ```
 
 If `@article.author_id` is 1, this would return:
@@ -1162,7 +1162,7 @@ Create a select tag and a series of contained option tags for the provided objec
 Example:
 
 ```ruby
-select("article", "person_id", Person.all.collect {|p| [ p.name, p.id ] }, {include_blank: true})
+select("article", "person_id", Person.all.collect { |p| [ p.name, p.id ] }, { include_blank: true })
 ```
 
 If `@article.person_id` is 1, this would become:
@@ -1225,7 +1225,7 @@ Creates a field set for grouping HTML form elements.
 Creates a file upload field.
 
 ```html+erb
-<%= form_tag({action:"post"}, multipart: true) do %>
+<%= form_tag({ action: "post" }, multipart: true) do %>
   <label for="file">File to Upload</label> <%= file_field_tag "file" %>
   <%= submit_tag %>
 <% end %>
diff --git a/guides/source/active_record_migrations.md b/guides/source/active_record_migrations.md
index 0e6c8c4f4a..7a994cc5de 100644
--- a/guides/source/active_record_migrations.md
+++ b/guides/source/active_record_migrations.md
@@ -357,7 +357,7 @@ will append `ENGINE=BLACKHOLE` to the SQL statement used to create the table
 
 ### Creating a Join Table
 
-Migration method `create_join_table` creates a HABTM join table. A typical use
+Migration method `create_join_table` creates an HABTM join table. A typical use
 would be:
 
 ```ruby
@@ -425,7 +425,7 @@ change_column :products, :part_number, :text
 This changes the column `part_number` on products table to be a `:text` field.
 
 Besides `change_column`, the `change_column_null` and `change_column_default`
-methods are used specifically to change the null and default values of a
+methods are used specifically to change a not null constraint and default values of a
 column.
 
 ```ruby
@@ -501,7 +501,7 @@ If the helpers provided by Active Record aren't enough you can use the `execute`
 method to execute arbitrary SQL:
 
 ```ruby
-Product.connection.execute('UPDATE `products` SET `price`=`free` WHERE 1')
+Product.connection.execute("UPDATE products SET price = 'free' WHERE 1=1")
 ```
 
 For more details and examples of individual methods, check the API documentation.
@@ -539,6 +539,14 @@ definitions:
 `change_table` is also reversible, as long as the block does not call `change`,
 `change_default` or `remove`.
 
+`remove_column` is reversible if you supply the column type as the third
+argument. Provide the original column options too, otherwise Rails can't
+recreate the column exactly when rolling back:
+
+```ruby
+remove_column :posts, :slug, :string, null: false, default: '', index: true
+```
+
 If you're going to need to use any other methods, you should use `reversible`
 or write the `up` and `down` methods instead of using the `change` method.
 
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md
index bef903b751..98fb566222 100644
--- a/guides/source/active_record_querying.md
+++ b/guides/source/active_record_querying.md
@@ -655,7 +655,7 @@ GROUP BY status
 Having
 ------
 
-SQL uses the `HAVING` clause to specify conditions on the `GROUP BY` fields. You can add the `HAVING` clause to the SQL fired by the `Model.find` by adding the `:having` option to the find.
+SQL uses the `HAVING` clause to specify conditions on the `GROUP BY` fields. You can add the `HAVING` clause to the SQL fired by the `Model.find` by adding the `having` method to the find.
 
 For example:
 
@@ -1343,7 +1343,7 @@ Client.unscoped {
 Dynamic Finders
 ---------------
 
-For every field (also known as an attribute) you define in your table, Active Record provides a finder method. If you have a field called `first_name` on your `Client` model for example, you get `find_by_first_name` for free from Active Record. If you have a `locked` field on the `Client` model, you also get `find_by_locked` and methods.
+For every field (also known as an attribute) you define in your table, Active Record provides a finder method. If you have a field called `first_name` on your `Client` model for example, you get `find_by_first_name` for free from Active Record. If you have a `locked` field on the `Client` model, you also get `find_by_locked` method.
 
 You can specify an exclamation point (`!`) on the end of the dynamic finders to get them to raise an `ActiveRecord::RecordNotFound` error if they do not return any records, like `Client.find_by_name!("Ryan")`
 
diff --git a/guides/source/active_record_validations.md b/guides/source/active_record_validations.md
index f19934fe89..d251c5c0b1 100644
--- a/guides/source/active_record_validations.md
+++ b/guides/source/active_record_validations.md
@@ -1055,7 +1055,9 @@ person.errors[:name]
 
 ### `errors.add`
 
-The `add` method lets you manually add messages that are related to particular attributes. You can use the `errors.full_messages` or `errors.to_a` methods to view the messages in the form they might be displayed to a user. Those particular messages get the attribute name prepended (and capitalized). `add` receives the name of the attribute you want to add the message to, and the message itself.
+The `add` method lets you add an error message related to a particular attribute. It takes as arguments the attribute and the error message.
+
+The `errors.full_messages` method (or its equivalent, `errors.to_a`) returns the error messages in a user-friendly format, with the capitalized attribute name prepended to each message, as shown in the examples below.
 
 ```ruby
 class Person < ActiveRecord::Base
@@ -1073,12 +1075,12 @@ person.errors.full_messages
  # => ["Name cannot contain the characters !@#%*()_-+="]
 ```
 
-Another way to do this is using `[]=` setter
+An equivalent to `errors#add` is to use `<<` to append a message to the `errors.messages` array for an attribute:
 
 ```ruby
   class Person < ActiveRecord::Base
     def a_method_used_for_validation_purposes
-      errors.add(:name, "cannot contain the characters !@#%*()_-+=")
+      errors.messages[:name] << "cannot contain the characters !@#%*()_-+="
     end
   end
 
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index 66626f41d1..5fb577e256 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -475,7 +475,7 @@ The methods `silence_warnings` and `enable_warnings` change the value of `$VERBO
 silence_warnings { Object.const_set "RAILS_DEFAULT_LOGGER", logger }
 ```
 
-Silencing exceptions is also possible with `suppress`. This method receives an arbitrary number of exception classes. If an exception is raised during the execution of the block and is `kind_of?` any of the arguments, `suppress` captures it and returns silently. Otherwise the exception is reraised:
+Silencing exceptions is also possible with `suppress`. This method receives an arbitrary number of exception classes. If an exception is raised during the execution of the block and is `kind_of?` any of the arguments, `suppress` captures it and returns silently. Otherwise the exception is not captured:
 
 ```ruby
 # If the user is locked, the increment is lost, no big deal.
@@ -506,6 +506,8 @@ Extensions to `Module`
 
 ### `alias_method_chain`
 
+**This method is deprecated in favour of using Module#prepend.**
+
 Using plain Ruby you can wrap methods with other methods, that's called _alias chaining_.
 
 For example, let's say you'd like params to be strings in functional tests, as they are in real requests, but still want the convenience of assigning integers and other kind of values. To accomplish that you could wrap `ActionController::TestCase#process` this way in `test/test_helper.rb`:
@@ -550,8 +552,6 @@ ActionController::TestCase.class_eval do
 end
 ```
 
-Rails uses `alias_method_chain` all over the code base. For example validations are added to `ActiveRecord::Base#save` by wrapping the method that way in a separate module specialized in validations.
-
 NOTE: Defined in `active_support/core_ext/module/aliasing.rb`.
 
 ### Attributes
diff --git a/guides/source/asset_pipeline.md b/guides/source/asset_pipeline.md
index 816bff3784..9da0ef1eb3 100644
--- a/guides/source/asset_pipeline.md
+++ b/guides/source/asset_pipeline.md
@@ -667,8 +667,7 @@ anymore, delete these options from the `javascript_include_tag` and
 `stylesheet_link_tag`.
 
 The fingerprinting behavior is controlled by the `config.assets.digest`
-initialization option (which defaults to `true` for production and `false` for
-everything else).
+initialization option (which defaults to `true` for production and development).
 
 NOTE: Under normal circumstances the default `config.assets.digest` option
 should not be changed. If there are no digests in the filenames, and far-future
diff --git a/guides/source/command_line.md b/guides/source/command_line.md
index d153e0bfa6..b409f20122 100644
--- a/guides/source/command_line.md
+++ b/guides/source/command_line.md
@@ -402,7 +402,7 @@ INFO: You can also use `rake -T`  to get the list of tasks.
 $ bin/rake about
 About your application's environment
 Rails version             5.0.0
-Ruby version              2.2.0 (x86_64-linux)
+Ruby version              2.2.1 (x86_64-linux)
 RubyGems version          2.4.5
 Rack version              1.6
 JavaScript Runtime        Node.js (V8)
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index 67285030a9..c6f6ef6dd5 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -309,6 +309,11 @@ All these configuration options are delegated to the `I18n` library.
 
 * `config.active_record.belongs_to_required_by_default` is a boolean value and controls whether `belongs_to` association is required by default.
 
+* `config.active_record.warn_on_records_fetched_greater_than` allows setting a
+  warning threshold for query result size. If the number of records returned
+  by a query exceeds the threshold, a warning is logged. This can be used to
+  identify queries which might be causing memory bloat.
+
 The MySQL adapter adds one additional configuration option:
 
 * `ActiveRecord::ConnectionAdapters::MysqlAdapter.emulate_booleans` controls whether Active Record will consider all `tinyint(1)` columns in a MySQL database to be booleans and is true by default.
@@ -826,15 +831,6 @@ server {
 
 Be sure to read the [NGINX documentation](http://nginx.org/en/docs/) for the most up-to-date information.
 
-#### Considerations when deploying to a subdirectory
-
-Deploying to a subdirectory in production has implications on various parts of
-Rails.
-
-* development environment:
-* testing environment:
-* serving static assets:
-* asset pipeline:
 
 Rails Environment Settings
 --------------------------
diff --git a/guides/source/form_helpers.md b/guides/source/form_helpers.md
index c21a2ba613..853227e2a1 100644
--- a/guides/source/form_helpers.md
+++ b/guides/source/form_helpers.md
@@ -241,7 +241,7 @@ Upon form submission the value entered by the user will be stored in `params[:pe
 
 WARNING: You must pass the name of an instance variable, i.e. `:person` or `"person"`, not an actual instance of your model object.
 
-Rails provides helpers for displaying the validation errors associated with a model object. These are covered in detail by the [Active Record Validations](./active_record_validations.html#displaying-validation-errors-in-views) guide.
+Rails provides helpers for displaying the validation errors associated with a model object. These are covered in detail by the [Active Record Validations](active_record_validations.html#displaying-validation-errors-in-views) guide.
 
 ### Binding a Form to an Object
 
@@ -282,7 +282,7 @@ The resulting HTML is:
 </form>
 ```
 
-The name passed to `form_for` controls the key used in `params` to access the form's values. Here the name is `article` and so all the inputs have names of the form `article[attribute_name]`. Accordingly, in the `create` action `params[:article]` will be a hash with keys `:title` and `:body`. You can read more about the significance of input names in the parameter_names section.
+The name passed to `form_for` controls the key used in `params` to access the form's values. Here the name is `article` and so all the inputs have names of the form `article[attribute_name]`. Accordingly, in the `create` action `params[:article]` will be a hash with keys `:title` and `:body`. You can read more about the significance of input names in the [parameter_names section](#understanding-parameter-naming-conventions).
 
 The helper methods called on the form builder are identical to the model object helpers except that it is not necessary to specify which object is being edited since this is already managed by the form builder.
 
diff --git a/guides/source/getting_started.md b/guides/source/getting_started.md
index fe01088b2e..db4e81e32e 100644
--- a/guides/source/getting_started.md
+++ b/guides/source/getting_started.md
@@ -1510,7 +1510,7 @@ comments on articles.
 
 We're going to see the same generator that we used before when creating
 the `Article` model. This time we'll create a `Comment` model to hold
-reference of article comments. Run this command in your terminal:
+reference to an article. Run this command in your terminal:
 
 ```bash
 $ bin/rails generate model Comment commenter:string body:text article:references
@@ -1522,7 +1522,7 @@ This command will generate four files:
 | -------------------------------------------- | ------------------------------------------------------------------------------------------------------ |
 | db/migrate/20140120201010_create_comments.rb | Migration to create the comments table in your database (your name will include a different timestamp) |
 | app/models/comment.rb                        | The Comment model                                                                                      |
-| test/models/comment_test.rb                  | Testing harness for the comments model                                                                 |
+| test/models/comment_test.rb                  | Testing harness for the comment model                                                                 |
 | test/fixtures/comments.yml                   | Sample comments for use in testing                                                                     |
 
 First, take a look at `app/models/comment.rb`:
diff --git a/guides/source/routing.md b/guides/source/routing.md
index 1a614fe42b..4ccc50a4d9 100644
--- a/guides/source/routing.md
+++ b/guides/source/routing.md
@@ -807,6 +807,18 @@ As long as `Sprockets` responds to `call` and returns a `[status, headers, body]
 
 NOTE: For the curious, `'articles#index'` actually expands out to `ArticlesController.action(:index)`, which returns a valid Rack application.
 
+If you specify a rack application as the endpoint for a matcher remember that the route will be unchanged in the receiving application. With the following route your rack application should expect the route to be '/admin':
+
+```ruby
+match '/admin', to: AdminApp, via: :all
+```
+
+If you would prefer to have your rack application receive requests at the root path instead use mount:
+
+```ruby
+mount AdminApp, at: '/admin'
+```
+
 ### Using `root`
 
 You can specify what Rails should route `'/'` to with the `root` method:
@@ -909,7 +921,7 @@ The `:as` option lets you override the normal naming for the named route helpers
 resources :photos, as: 'images'
 ```
 
-will recognize incoming paths beginning with `/photos` and route the requests to `PhotosController`, but use the value of the :as option to name the helpers.
+will recognize incoming paths beginning with `/photos` and route the requests to `PhotosController`, but use the value of the `:as` option to name the helpers.
 
 | HTTP Verb | Path             | Controller#Action | Named Helper         |
 | --------- | ---------------- | ----------------- | -------------------- |
diff --git a/guides/source/security.md b/guides/source/security.md
index e486edde31..184af98d65 100644
--- a/guides/source/security.md
+++ b/guides/source/security.md
@@ -710,7 +710,7 @@ The log files on www.attacker.com will read like this:
 GET http://www.attacker.com/_app_session=836c1c25278e5b321d6bea4f19cb57e2
 ```
 
-You can mitigate these attacks (in the obvious way) by adding the [httpOnly](http://dev.rubyonrails.org/ticket/8895) flag to cookies, so that document.cookie may not be read by JavaScript. Http only cookies can be used from IE v6.SP1, Firefox v2.0.0.5 and Opera 9.5. Safari is still considering, it ignores the option. But other, older browsers (such as WebTV and IE 5.5 on Mac) can actually cause the page to fail to load. Be warned that cookies [will still be visible using Ajax](http://ha.ckers.org/blog/20070719/firefox-implements-httponly-and-is-vulnerable-to-xmlhttprequest/), though.
+You can mitigate these attacks (in the obvious way) by adding the **httpOnly** flag to cookies, so that document.cookie may not be read by JavaScript. Http only cookies can be used from IE v6.SP1, Firefox v2.0.0.5 and Opera 9.5. Safari is still considering, it ignores the option. But other, older browsers (such as WebTV and IE 5.5 on Mac) can actually cause the page to fail to load. Be warned that cookies [will still be visible using Ajax](http://ha.ckers.org/blog/20070719/firefox-implements-httponly-and-is-vulnerable-to-xmlhttprequest/), though.
 
 ##### Defacement
 
diff --git a/guides/source/testing.md b/guides/source/testing.md
index 008a485720..752ef48b16 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -59,9 +59,9 @@ You can find comprehensive documentation in the [Fixtures API documentation](htt
 
 #### What Are Fixtures?
 
-_Fixtures_ is a fancy word for sample data. Fixtures allow you to populate your testing database with predefined data before your tests run. Fixtures are database independent written in YAML. There is one file per model.
+_Fixtures_ is a fancy word for sample data. Fixtures allow you to populate your testing database with predefined data before your tests run. Fixtures are database independent and written in YAML. There is one file per model.
 
-You'll find fixtures under your `test/fixtures` directory. When you run `rails generate model` to create a new model fixture stubs will be automatically created and placed in this directory.
+You'll find fixtures under your `test/fixtures` directory. When you run `rails generate model` to create a new model, Rails automatically creates fixture stubs in this directory.
 
 #### YAML
 
@@ -162,7 +162,7 @@ project is created.
 
 We will cover each of types Rails tests listed above in this guide.
 
-Unit Testing your Models
+Model Testing
 ------------------------
 
 In Rails, unit tests are what you write to test your models.
@@ -929,7 +929,7 @@ assert_select_email do
 end
 ```
 
-Testing helpers
+Testing Helpers
 ---------------
 
 In order to test helpers, all you need to do is check that the output of the
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index 05c46a9e76..5a6f267360 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -75,6 +75,21 @@ warning by adding the following configuration to your `config/application.rb`:
 
 See [#17227](https://github.com/rails/rails/pull/17227) for more details.
 
+### ActiveJob jobs now inherent from ApplicationJob by default
+
+In Rails 4.2 an ActiveJob inherents from `ActiveJob::Base`. In Rails 5.0 this
+behaviour has changed to now inherent from `ApplicationJob`.
+
+When upgrading from Rails 4.2 to Rails 5.0 you need to create a file
+`application_job.rb` in `app/jobs/` and add the following content:
+
+```
+class ApplicationJob < ActiveJob::Base
+end
+```
+
+See [#19034](https://github.com/rails/rails/pull/19034) for more details
+
 Upgrading from Rails 4.1 to Rails 4.2
 -------------------------------------