21 files changed, 240 insertions, 68 deletions
diff --git a/guides/source/4_0_release_notes.md b/guides/source/4_0_release_notes.md
index 66e26c63cb..006d0cda92 100644
--- a/guides/source/4_0_release_notes.md
+++ b/guides/source/4_0_release_notes.md
@@ -50,10 +50,47 @@ $ ruby /path/to/rails/railties/bin/rails new myapp --dev
 Major Features
 --------------
 
-TODO. Give a list and then talk about each of them briefly. We can point to relevant code commits or documentation from these sections.
-
 [![Rails 4.0](images/rails4_features.png)](http://guides.rubyonrails.org/images/rails4_features.png)
 
+### 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.
+
+### 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)) - Set ETag and Last-Modified headers using `etag` and `fresh_when`.
+ * **[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 is moved outside of ActionPack.
+ * **Do not depend on ActiveModel** ([commit](https://github.com/rails/rails/commit/166dbaa7526a96fdf046f093f25b0a134b277a68)) - ActionPack no longer depends on ActiveModel.
+
+### General
+
+ * **ActiveModel::Model** ([commit](https://github.com/rails/rails/commit/3b822e91d1a6c4eab0064989bbd07aae3a6d0d08)) - `ActiveModel::Model` is extracted from ActiveRecord. `ActiveModel::Model` provides validations and `form_for` for normal Ruby objects.
+ * **New scope API** ([commit](https://github.com/rails/rails/commit/50cbc03d18c5984347965a94027879623fc44cce)) - Scopes must always use callables.
+ * **Schema cache dump** ([commit](https://github.com/rails/rails/commit/5ca4fc95818047108e69e22d200e7a4a22969477)) - To improve Rails boot time, instead of loading the schema directly from the database, load the schema from a dump file.
+ * **Support for specifying transaction isolation level** ([commit](https://github.com/rails/rails/commit/392eeecc11a291e406db927a18b75f41b2658253)) - Choose whether repeatable reads or improved performance (less locking) is more important.
+ * **Dalli** ([commit](https://github.com/rails/rails/commit/82663306f428a5bbc90c511458432afb26d2f238)) - For the memcache session store, use the Dalli memcache client.
+ * **Notifications start &amp; finish** ([commit](https://github.com/rails/rails/commit/f08f8750a512f741acb004d0cebe210c5f949f28)) - Active Support instrumentation reports start and finish notifications to subscribers.
+ * **Thread safe by default** ([commit](https://github.com/rails/rails/commit/5d416b907864d99af55ebaa400fff217e17570cd)) - Rails can run in threaded app servers without additional configuration. Note: Check that the gems you are using are threadsafe.
+ * **PATCH verb** ([commit](https://github.com/rails/rails/commit/eed9f2539e3ab5a68e798802f464b8e4e95e619e)) - In Rails, PATCH replaces PUT. PATCH is used for partial updates of resources.
+
+### 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).
+ 
 Extraction of features to gems
 ---------------------------
 
diff --git a/guides/source/action_controller_overview.md b/guides/source/action_controller_overview.md
index f2abd833aa..ecaee02cce 100644
--- a/guides/source/action_controller_overview.md
+++ b/guides/source/action_controller_overview.md
@@ -907,6 +907,92 @@ Now the user can request to get a PDF version of a client just by adding ".pdf"
 GET /clients/1.pdf
 ```
 
+### Live Streaming of Arbitrary Data
+
+Rails allows you to stream more than just files. In fact, you can stream anything
+you would like in a response object. The `ActionController::Live` module allows
+you to create a persistent connection with a browser. Using this module, you will
+be able to send arbitrary data to the browser at specific points in time.
+
+#### Incorporating Live Streaming
+
+Including `ActionController::Live` inside of your controller class will provide
+all actions inside of the controller the ability to stream data. You can mix in
+the module like so:
+
+```ruby
+class MyController < ActionController::Base
+  include ActionController::Live
+
+  def stream
+    response.headers['Content-Type'] = 'text/event-stream'
+    100.times {
+      response.stream.write "hello world\n"
+      sleep 1
+    }
+  ensure
+    response.stream.close
+  end
+end
+```
+
+The above code will keep a persistent connection with the browser and send 100
+messages of `"hello world\n"`, each one second apart.
+
+There are a couple of things to notice in the above example. We need to make
+sure to close the response stream. Forgetting to close the stream will leave
+the socket open forever. We also have to set the content type to `text/event-stream`
+before we write to the response stream. This is because headers cannot be written
+after the response has been committed (when `response.committed` returns a truthy
+value), which occurs when you `write` or `commit` the response stream.
+
+#### Example Usage
+
+Let's suppose that you were making a Karaoke machine and a user wants to get the
+lyrics for a particular song. Each `Song` has a particular number of lines and
+each line takes time `num_beats` to finish singing.
+
+If we wanted to return the lyrics in Karaoke fashion (only sending the line when
+the singer has finished the previous line), then we could use `ActionController::Live`
+as follows:
+
+```ruby
+class LyricsController < ActionController::Base
+  include ActionController::Live
+
+  def show
+    response.headers['Content-Type'] = 'text/event-stream'
+    song = Song.find(params[:id])
+
+    song.each do |line|
+      response.stream.write line.lyrics
+      sleep line.num_beats
+    end
+  ensure
+    response.stream.close
+  end
+end
+```
+
+The above code sends the next line only after the singer has completed the previous
+line.
+
+#### Streaming Considerations
+
+Streaming arbitrary data is an extremely powerful tool. As shown in the previous
+examples, you can choose when and what to send across a response stream. However,
+you should also note the following things:
+
+* Each response stream creates a new thread and copies over the thread local
+  variables from the original thread. Having too many thread local variables can
+  negatively impact performance. Similarly, a large number of threads can also
+  hinder performance.
+* Failing to close the response stream will leave the corresponding socket open
+  forever. Make sure to call `close` whenever you are using a response stream.
+* WEBrick servers buffer all responses, and so including `ActionController::Live`
+  will not work. You must use a web server which does not automatically buffer 
+  responses.
+
 Log Filtering
 -------------
 
diff --git a/guides/source/action_view_overview.md b/guides/source/action_view_overview.md
index bdb51d881d..3542844f33 100644
--- a/guides/source/action_view_overview.md
+++ b/guides/source/action_view_overview.md
@@ -775,8 +775,8 @@ select_day(5)
 Returns a select tag with options for each of the hours 0 through 23 with the current hour selected.
 
 ```ruby
-# Generates a select field for minutes that defaults to the minutes for the time provided
-select_minute(Time.now + 6.hours)
+# Generates a select field for hours that defaults to the hours for the time provided
+select_hour(Time.now + 6.hours)
 ```
 
 #### select_minute
@@ -941,9 +941,9 @@ Creates a form and a scope around a specific model object that is used as a base
 ```html+erb
 <%= form_for @post do |f| %>
   <%= f.label :title, 'Title' %>:
-  <%= f.text_field :title %><br />
+  <%= f.text_field :title %><br>
   <%= f.label :body, 'Body' %>:
-  <%= f.text_area :body %><br />
+  <%= f.text_area :body %><br>
 <% end %>
 ```
 
@@ -1492,7 +1492,7 @@ number_to_human_size(1234567)       # => 1.2 MB
 Formats a number as a percentage string.
 
 ```ruby
-number_to_percentage(100, :precision => 0)        # => 100%
+number_to_percentage(100, precision: 0)        # => 100%
 ```
 
 #### number_to_phone
diff --git a/guides/source/active_record_basics.md b/guides/source/active_record_basics.md
index d9fb20f3bf..556c2544ff 100644
--- a/guides/source/active_record_basics.md
+++ b/guides/source/active_record_basics.md
@@ -105,7 +105,7 @@ depending on the purpose of these columns.
   Migrations](migrations.html) to create your tables, this column will be
   automatically created.
 
-There are also some optional column names that will create additional features
+There are also some optional column names that will add additional features
 to Active Record instances:
 
 * `created_at` - Automatically gets set to the current date and time when the
@@ -343,7 +343,7 @@ Migrations
 
 Rails provides a domain-specific language for managing a database schema called
 migrations. Migrations are stored in files which are executed against any
-database that Active Record support using `rake`. Here's a migration that
+database that Active Record supports using `rake`. Here's a migration that
 creates a table:
 
 ```ruby
diff --git a/guides/source/active_record_callbacks.md b/guides/source/active_record_callbacks.md
index 01401cc340..df1dd22971 100644
--- a/guides/source/active_record_callbacks.md
+++ b/guides/source/active_record_callbacks.md
@@ -49,8 +49,8 @@ The macro-style class methods can also receive a block. Consider using this styl
 class User < ActiveRecord::Base
   validates :login, :email, presence: true
 
-  before_create do |user|
-    user.name = user.login.capitalize if user.name.blank?
+  before_create do
+    self.name = login.capitalize if name.blank?
   end
 end
 ```
@@ -343,7 +343,7 @@ By using the `after_commit` callback we can account for this case.
 
 ```ruby
 class PictureFile < ActiveRecord::Base
-  after_commit :delete_picture_file_from_disk, :on => [:destroy]
+  after_commit :delete_picture_file_from_disk, on: [:destroy]
 
   def delete_picture_file_from_disk
     if File.exist?(filepath)
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md
index 031a203f08..0592821a14 100644
--- a/guides/source/active_record_querying.md
+++ b/guides/source/active_record_querying.md
@@ -711,7 +711,7 @@ Post.order('id DESC').limit(20).unscope(:order, :limit) = Post.all
 You can additionally unscope specific where clauses. For example:
 
 ```ruby
-Post.where(:id => 10).limit(1).unscope(where: :id, :limit).order('id DESC') = Post.order('id DESC')
+Post.where(id: 10).limit(1).unscope({ where: :id }, :limit).order('id DESC') = Post.order('id DESC')
 ```
 
 ### `only`
diff --git a/guides/source/active_record_validations.md b/guides/source/active_record_validations.md
index 3bfc600e7c..d95b587e78 100644
--- a/guides/source/active_record_validations.md
+++ b/guides/source/active_record_validations.md
@@ -121,7 +121,7 @@ database only if the object is valid:
 
 The bang versions (e.g. `save!`) raise an exception if the record is invalid.
 The non-bang versions don't, `save` and `update` return `false`,
-`create` just return the objects.
+`create` just returns the object.
 
 ### Skipping Validations
 
diff --git a/guides/source/asset_pipeline.md b/guides/source/asset_pipeline.md
index b68c24acfd..6c4d7fe255 100644
--- a/guides/source/asset_pipeline.md
+++ b/guides/source/asset_pipeline.md
@@ -69,12 +69,12 @@ Rails' old strategy was to append a date-based query string to every asset linke
 
 The query string strategy has several disadvantages:
 
-1. **Not all caches will reliably cache content where the filename only differs by query parameters**<br />
+1. **Not all caches will reliably cache content where the filename only differs by query parameters**<br>
     [Steve Souders recommends](http://www.stevesouders.com/blog/2008/08/23/revving-filenames-dont-use-querystring/), "...avoiding a querystring for cacheable resources". He found that in this case 5-20% of requests will not be cached. Query strings in particular do not work at all with some CDNs for cache invalidation.
 
-2. **The file name can change between nodes in multi-server environments.**<br />
+2. **The file name can change between nodes in multi-server environments.**<br>
     The default query string in Rails 2.x is based on the modification time of the files. When assets are deployed to a cluster, there is no guarantee that the timestamps will be the same, resulting in different values being used depending on which server handles the request.
-3. **Too much cache invalidation**<br />
+3. **Too much cache invalidation**<br>
     When static assets are deployed with each new release of code, the mtime(time of last modification) of _all_ these files changes, forcing all remote clients to fetch them again, even when the content of those assets has not changed.
 
 Fingerprinting fixes these problems by avoiding query strings, and by ensuring that filenames are consistent based on their content.
@@ -606,7 +606,7 @@ Customizing the Pipeline
 
 ### CSS Compression
 
-There is currently one option for compressing CSS, YUI. The [YUI CSS compressor](http://developer.yahoo.com/yui/compressor/css.html) provides minification.
+There is currently one option for compressing CSS, YUI. The [YUI CSS compressor](http://yui.github.io/yuicompressor/css.html) provides minification.
 
 The following line enables YUI compression, and requires the `yui-compressor` gem.
 
@@ -620,7 +620,7 @@ The `config.assets.compress` must be set to `true` to enable CSS compression.
 
 Possible options for JavaScript compression are `:closure`, `:uglifier` and `:yui`. These require the use of the `closure-compiler`, `uglifier` or `yui-compressor` gems, respectively.
 
-The default Gemfile includes [uglifier](https://github.com/lautis/uglifier). This gem wraps [UglifierJS](https://github.com/mishoo/UglifyJS) (written for NodeJS) in Ruby. It compresses your code by removing white space. It also includes other optimizations such as changing your `if` and `else` statements to ternary operators where possible.
+The default Gemfile includes [uglifier](https://github.com/lautis/uglifier). This gem wraps [UglifyJS](https://github.com/mishoo/UglifyJS) (written for NodeJS) in Ruby. It compresses your code by removing white space and comments, shortening local variable names, and performing other micro-optimizations such as changing `if` and `else` statements to ternary operators where possible.
 
 The following line invokes `uglifier` for JavaScript compression.
 
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md
index 884aa6a9ea..e6a66f3fa1 100644
--- a/guides/source/association_basics.md
+++ b/guides/source/association_basics.md
@@ -953,7 +953,7 @@ end
 
 ##### `includes`
 
-You can use the `includes` method let you specify second-order associations that should be eager-loaded when this association is used. For example, consider these models:
+You can use the `includes` method to specify second-order associations that should be eager-loaded when this association is used. For example, consider these models:
 
 ```ruby
 class LineItem < ActiveRecord::Base
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index 9bb5d621fc..2f5444c763 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -103,6 +103,8 @@ numbers. New applications filter out passwords by adding the following `config.f
 
 * `config.force_ssl` forces all requests to be under HTTPS protocol by using `ActionDispatch::SSL` middleware.
 
+* `config.log_formatter` defines the formatter of the Rails logger. This option defaults to a instance of `ActiveSupport::Logger::SimpleFormatter` for all modes except production, where it defaults to `Logger::Formatter`.
+
 * `config.log_level` defines the verbosity of the Rails logger. This option defaults to `:debug` for all modes except production, where it defaults to `:info`.
 
 * `config.log_tags` accepts a list of methods that respond to `request` object. This makes it easy to tag log lines with debug information like subdomain and request id — both very helpful in debugging multi-user production applications.
diff --git a/guides/source/contributing_to_ruby_on_rails.md b/guides/source/contributing_to_ruby_on_rails.md
index b9f42fa51b..24e16ecd40 100644
--- a/guides/source/contributing_to_ruby_on_rails.md
+++ b/guides/source/contributing_to_ruby_on_rails.md
@@ -234,8 +234,8 @@ workflow with the [rails-dev-box](https://github.com/rails/rails-dev-box).
 
 As a compromise, test what your code obviously affects, and if the change is
 not in railties run the whole test suite of the affected component. If all is
-green that's enough to propose your contribution. We have [Travis CI](https
-://travis-ci.org/) as a safety net for catching unexpected breakages
+green that's enough to propose your contribution. We have [Travis CI](https://travis-ci.org/rails/rails)
+as a safety net for catching unexpected breakages
 elsewhere.
 
 TIP: Changes that are cosmetic in nature and do not add anything substantial to the stability, functionality, or testability of Rails will generally not be accepted.
diff --git a/guides/source/engines.md b/guides/source/engines.md
index d8120fe244..a77be917a2 100644
--- a/guides/source/engines.md
+++ b/guides/source/engines.md
@@ -346,7 +346,7 @@ Next, the partial that this line will render needs to exist. Create a new direct
 <h3>New comment</h3>
 <%= form_for [@post, @post.comments.build] do |f| %>
   <p>
-    <%= f.label :text %><br />
+    <%= f.label :text %><br>
     <%= f.text_area :text %>
   </p>
   <%= f.submit %>
@@ -520,7 +520,7 @@ First, the `author_name` text field needs to be added to the `app/views/blorgh/p
 
 ```html+erb
 <div class="field">
-  <%= f.label :author_name %><br />
+  <%= f.label :author_name %><br>
   <%= f.text_field :author_name %>
 </div>
 ```
diff --git a/guides/source/form_helpers.md b/guides/source/form_helpers.md
index 7f37a298b1..11e8db9e88 100644
--- a/guides/source/form_helpers.md
+++ b/guides/source/form_helpers.md
@@ -553,7 +553,7 @@ outputs (with actual option values omitted for brevity)
 which results in a `params` hash like
 
 ```ruby
-{:person => {'birth_date(1i)' => '2008', 'birth_date(2i)' => '11', 'birth_date(3i)' => '22'}}
+{'person' => {'birth_date(1i)' => '2008', 'birth_date(2i)' => '11', 'birth_date(3i)' => '22'}}
 ```
 
 When this is passed to `Person.new` (or `update`), Active Record spots that these parameters should all be used to construct the `birth_date` attribute and uses the suffixed information to determine in which order it should pass these parameters to functions such as `Date.civil`.
@@ -881,19 +881,19 @@ end
 
 ```ruby
 {
-    :person => {
-        :name => 'John Doe',
-        :addresses_attributes => {
-            '0' => {
-                :kind => 'Home',
-                :street => '221b Baker Street',
-            },
-            '1' => {
-                :kind => 'Office',
-                :street => '31 Spooner Street'
-            }
-        }
+  'person' => {
+    'name' => 'John Doe',
+    'addresses_attributes' => {
+      '0' => {
+        'kind' => 'Home',
+        'street' => '221b Baker Street'
+      },
+      '1' => {
+        'kind' => 'Office',
+        'street' => '31 Spooner Street'
+      }
     }
+  }
 }
 ```
 
diff --git a/guides/source/getting_started.md b/guides/source/getting_started.md
index cdb25a1013..a0e0975d62 100644
--- a/guides/source/getting_started.md
+++ b/guides/source/getting_started.md
@@ -138,7 +138,7 @@ application. Most of the work in this tutorial will happen in the `app/` folder,
 |config/|Configure your application's runtime rules, routes, database, and more. This is covered in more detail in [Configuring Rails Applications](configuring.html)|
 |config.ru|Rack configuration for Rack based servers used to start the application.|
 |db/|Contains your current database schema, as well as the database migrations.|
-|Gemfile<br />Gemfile.lock|These files allow you to specify what gem dependencies are needed for your Rails application. These files are used by the Bundler gem. For more information about Bundler, see [the Bundler website](http://gembundler.com) |
+|Gemfile<br>Gemfile.lock|These files allow you to specify what gem dependencies are needed for your Rails application. These files are used by the Bundler gem. For more information about Bundler, see [the Bundler website](http://gembundler.com) |
 |lib/|Extended modules for your application.|
 |log/|Application log files.|
 |public/|The only folder seen to the world as-is. Contains the static files and compiled assets.|
@@ -264,11 +264,14 @@ Blog::Application.routes.draw do
 end
 ```
 
-If you run `rake routes`, you'll see that all the routes for the
-standard RESTful actions.
+If you run `rake routes`, you'll see that it has defined routes for all the
+standard RESTful actions.  The meaning of the prefix column (and other columns)
+will be seen later, but for now notice that Rails has inferred the
+singular form `post` and makes meaningful use of the distinction.
 
 ```bash
 $ rake routes
+   Prefix Verb   URI Pattern               Controller#Action
     posts GET    /posts(.:format)          posts#index
           POST   /posts(.:format)          posts#create
  new_post GET    /posts/new(.:format)      posts#new
@@ -394,9 +397,27 @@ Edit the `form_for` line inside `app/views/posts/new.html.erb` to look like this
 <%= form_for :post, url: posts_path do |f| %>
 ```
 
-In this example, the `posts_path` helper is passed to the `:url` option. What Rails will do with this is that it will point the form to the `create` action of the current controller, the `PostsController`, and will send a `POST` request to that route.
-
-By using the `post` method rather than the `get` method, Rails will define a route that will only respond to POST methods. The POST method is the typical method used by forms all over the web.
+In this example, the `posts_path` helper is passed to the `:url` option.
+To see what Rails will do with this, we look back at the output of
+`rake routes`:
+```bash
+$ rake routes
+   Prefix Verb   URI Pattern               Controller#Action
+    posts GET    /posts(.:format)          posts#index
+          POST   /posts(.:format)          posts#create
+ new_post GET    /posts/new(.:format)      posts#new
+edit_post GET    /posts/:id/edit(.:format) posts#edit
+     post GET    /posts/:id(.:format)      posts#show
+          PATCH  /posts/:id(.:format)      posts#update
+          PUT    /posts/:id(.:format)      posts#update
+          DELETE /posts/:id(.:format)      posts#destroy
+     root        /                         welcome#index
+```
+The `posts_path` helper tells Rails to point the form
+to the URI Pattern associated with the `posts` prefix; and
+the form will (by default) send a `POST` request
+to that route.  This is associated with the 
+`create` action of the current controller, the `PostsController`.
 
 With the form and its associated route defined, you will be able to fill in the form and then click the submit button to begin the process of creating a new post, so go ahead and do that. When you submit the form, you should see a familiar error:
 
@@ -723,7 +744,7 @@ TIP: In development mode (which is what you're working in by default), Rails
 reloads your application with every browser request, so there's no need to stop
 and restart the web server when a change is made.
 
-### Allowing the update of fields
+### Adding Some Validation
 
 The model file, `app/models/post.rb` is about as simple as it can get:
 
@@ -738,8 +759,6 @@ your Rails models for free, including basic database CRUD (Create, Read, Update,
 Destroy) operations, data validation, as well as sophisticated search support
 and the ability to relate multiple models to one another.
 
-### Adding Some Validation
-
 Rails includes methods to help you validate the data that you send to models.
 Open the `app/models/post.rb` file and edit it:
 
@@ -1018,9 +1037,14 @@ content:
 ```
 
 Everything except for the `form_for` declaration remained the same.
-How `form_for` can figure out the right `action` and `method` attributes when building the form
-will be explained in [just a moment](/form_helpers.html#binding-a-form-to-an-object).
-For now, let's update the `app/views/posts/new.html.erb` view to use this new partial, rewriting it
+The reason we can use this shorter, simpler `form_for` declaration 
+to stand in for either of the other forms is that `@post` is a *resource*
+corresponding to a full set of RESTful routes, and Rails is able to infer
+which URI and method to use.
+For more information about this use of `form_for`, see
+[Resource-oriented style](//api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-form_for-label-Resource-oriented+style).
+
+Now, let's update the `app/views/posts/new.html.erb` view to use this new partial, rewriting it
 completely:
 
 ```html+erb
@@ -1291,11 +1315,11 @@ So first, we'll wire up the Post show template
 <h2>Add a comment:</h2>
 <%= form_for([@post, @post.comments.build]) do |f| %>
   <p>
-    <%= f.label :commenter %><br />
+    <%= f.label :commenter %><br>
     <%= f.text_field :commenter %>
   </p>
   <p>
-    <%= f.label :body %><br />
+    <%= f.label :body %><br>
     <%= f.text_area :body %>
   </p>
   <p>
@@ -1371,11 +1395,11 @@ template. This is where we want the comment to show, so let's add that to the
 <h2>Add a comment:</h2>
 <%= form_for([@post, @post.comments.build]) do |f| %>
   <p>
-    <%= f.label :commenter %><br />
+    <%= f.label :commenter %><br>
     <%= f.text_field :commenter %>
   </p>
   <p>
-    <%= f.label :body %><br />
+    <%= f.label :body %><br>
     <%= f.text_area :body %>
   </p>
   <p>
@@ -1437,11 +1461,11 @@ following:
 <h2>Add a comment:</h2>
 <%= form_for([@post, @post.comments.build]) do |f| %>
   <p>
-    <%= f.label :commenter %><br />
+    <%= f.label :commenter %><br>
     <%= f.text_field :commenter %>
   </p>
   <p>
-    <%= f.label :body %><br />
+    <%= f.label :body %><br>
     <%= f.text_area :body %>
   </p>
   <p>
@@ -1467,11 +1491,11 @@ create a file `app/views/comments/_form.html.erb` containing:
 ```html+erb
 <%= form_for([@post, @post.comments.build]) do |f| %>
   <p>
-    <%= f.label :commenter %><br />
+    <%= f.label :commenter %><br>
     <%= f.text_field :commenter %>
   </p>
   <p>
-    <%= f.label :body %><br />
+    <%= f.label :body %><br>
     <%= f.text_area :body %>
   </p>
   <p>
diff --git a/guides/source/index.html.erb b/guides/source/index.html.erb
index a8e4525c67..57c224c165 100644
--- a/guides/source/index.html.erb
+++ b/guides/source/index.html.erb
@@ -19,7 +19,7 @@ Ruby on Rails Guides
   <h3><%= section['name'] %></h3>
   <dl>
     <% section['documents'].each do |document| %>
-      <%= guide(document['name'], document['url'], :work_in_progress => document['work_in_progress']) do %>
+      <%= guide(document['name'], document['url'], work_in_progress: document['work_in_progress']) do %>
         <p><%= document['description'] %></p>
       <% end %>
     <% end %>
diff --git a/guides/source/initialization.md b/guides/source/initialization.md
index 11c736585f..26259408b4 100644
--- a/guides/source/initialization.md
+++ b/guides/source/initialization.md
@@ -350,7 +350,7 @@ end
 
 The interesting part for a Rails app is the last line, `server.run`. Here we encounter the `wrapped_app` method again, which this time
 we're going to explore more (even though it was executed before, and
-thus memorized by now).
+thus memoized by now).
 
 ```ruby
 @wrapped_app ||= build_app app
diff --git a/guides/source/layout.html.erb b/guides/source/layout.html.erb
index c737a0e9dc..71d3c5638b 100644
--- a/guides/source/layout.html.erb
+++ b/guides/source/layout.html.erb
@@ -48,7 +48,7 @@
       <ul class="nav">
         <li><a class="nav-item" href="index.html">Home</a></li>
         <li class="guides-index guides-index-large">
-          <a href="index.html" onclick="guideMenu(); return false;" id="guidesMenu" class="guides-index-item nav-item">Guides Index</a>
+          <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| %>
@@ -143,7 +143,7 @@
   <script type="text/javascript" src="javascripts/syntaxhighlighter/shBrushSql.js"></script>
   <script type="text/javascript" src="javascripts/syntaxhighlighter/shBrushPlain.js"></script>
   <script type="text/javascript">
-    SyntaxHighlighter.all()
+    SyntaxHighlighter.all();
     $(guidesIndex.bind);
   </script>
 </body>
diff --git a/guides/source/layouts_and_rendering.md b/guides/source/layouts_and_rendering.md
index 5908801bc9..5b6e5387ff 100644
--- a/guides/source/layouts_and_rendering.md
+++ b/guides/source/layouts_and_rendering.md
@@ -88,7 +88,7 @@ If we want to display the properties of all the books in our view, we can do so
 <% end %>
 </table>
 
-<br />
+<br>
 
 <%= link_to "New book", new_book_path %>
 ```
@@ -1026,7 +1026,7 @@ You can also pass local variables into partials, making them even more powerful
     ```html+erb
     <%= form_for(zone) do |f| %>
       <p>
-        <b>Zone name</b><br />
+        <b>Zone name</b><br>
         <%= f.text_field :name %>
       </p>
       <p>
diff --git a/guides/source/migrations.md b/guides/source/migrations.md
index 035f9499de..e6d1e71f5e 100644
--- a/guides/source/migrations.md
+++ b/guides/source/migrations.md
@@ -376,7 +376,7 @@ create_join_table :products, :categories, column_options: {null: true}
 will create the `product_id` and `category_id` with the `:null` option as
 `true`.
 
-You can pass the option `:table_name` with you want to customize the table
+You can pass the option `:table_name` when you want to customize the table
 name. For example,
 
 ```ruby
@@ -841,7 +841,6 @@ class AddFlagToProduct < ActiveRecord::Migration
     reversible do |dir|
       dir.up { Product.update_all flag: false }
     end
-    Product.update_all flag: false
   end
 end
 ```
diff --git a/guides/source/rails_on_rack.md b/guides/source/rails_on_rack.md
index 73f541bda4..3becaccb0a 100644
--- a/guides/source/rails_on_rack.md
+++ b/guides/source/rails_on_rack.md
@@ -327,7 +327,7 @@ The following shows how to replace use `Rack::Builder` instead of the Rails supp
 config.middleware.clear
 ```
 
-<br />
+<br>
 <strong>Add a `config.ru` file to `Rails.root`</strong>
 
 ```ruby
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index 0f388d15c4..b7ec747a77 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -131,7 +131,15 @@ The following changes are meant for upgrading your application to Rails 4.0.
 
 ### Gemfile
 
-Rails 4.0 removed the `assets` group from Gemfile. You'd need to remove that line from your Gemfile when upgrading.
+Rails 4.0 removed the `assets` group from Gemfile. You'd need to remove that
+line from your Gemfile when upgrading. You should also update your application
+file (in `config/application.rb`):
+
+```ruby
+# Require the gems listed in Gemfile, including any gems
+# you've limited to :test, :development, or :production.
+Bundler.require(:default, Rails.env)
+```
 
 ### vendor/plugins
 
@@ -143,11 +151,16 @@ Rails 4.0 no longer supports loading plugins from `vendor/plugins`. You must rep
 
 * The `delete` method in collection associations can now receive `Fixnum` or `String` arguments as record ids, besides records, pretty much like the `destroy` method does. Previously it raised `ActiveRecord::AssociationTypeMismatch` for such arguments. From Rails 4.0 on `delete` automatically tries to find the records matching the given ids before deleting them.
 
+* In Rails 4.0 when a column or a table is renamed the related indexes are also renamed. If you have migrations which rename the indexes, they are no longer needed.
+
 * Rails 4.0 has changed how orders get stacked in `ActiveRecord::Relation`. In previous versions of Rails, the new order was applied after the previously defined order. But this is no longer true. Check [Active Record Query guide](active_record_querying.html#ordering) for more information.
 
 * Rails 4.0 has changed `serialized_attributes` and `attr_readonly` to class methods only. You shouldn't use instance methods since it's now deprecated. You should change them to use class methods, e.g. `self.serialized_attributes` to `self.class.serialized_attributes`.
 
-* Rails 4.0 has removed `attr_accessible` and `attr_protected` feature in favor of Strong Parameters. You can use the [Protected Attributes gem](https://github.com/rails/protected_attributes) to a smoothly upgrade path.
+* Rails 4.0 has removed `attr_accessible` and `attr_protected` feature in favor of Strong Parameters. You can use the [Protected Attributes gem](https://github.com/rails/protected_attributes) for a smooth upgrade path.
+
+* If you are not using Protected Attributes, you can remove any options related to
+this gem such as `whitelist_attributes` or `mass_assignment_sanitizer` options.
 
 * Rails 4.0 requires that scopes use a callable object such as a Proc or lambda:
 
@@ -208,6 +221,11 @@ Please read [Pull Request #9978](https://github.com/rails/rails/pull/9978) for d
 
 * Rails 4.0 deprecates the `dom_id` and `dom_class` methods in controllers (they are fine in views). You will need to include the `ActionView::RecordIdentifier` module in controllers requiring this feature.
 
+* Rails 4.0 deprecates the `:confirm` option for the `link_to` helper. You should
+instead rely on a data attribute (e.g. `data: { confirm: 'Are you sure?' }`).
+This deprecation also concerns the helpers based on this one (such as `link_to_if`
+or `link_to_unless`).
+
 * Rails 4.0 changed how `assert_generates`, `assert_recognizes`, and `assert_routing` work. Now all these assertions raise `Assertion` instead of `ActionController::RoutingError`.
 
 * Rails 4.0 raises an `ArgumentError` if clashing named routes are defined. This can be triggered by explicitly defined named routes or by the `resources` method. Here are two examples that clash with routes named `example_path`:
@@ -295,6 +313,12 @@ Active Record Observer and Action Controller Sweeper have been extracted to the
 ### sprockets-rails
 
 * `assets:precompile:primary` has been removed. Use `assets:precompile` instead.
+* The `config.assets.compress` option should be changed to
+`config.assets.js_compressor` like so for instance:
+
+```ruby
+config.assets.js_compressor = :uglifier
+```
 
 ### sass-rails