Merge branch 'master' of github.com:rails/rails

1 files changed, 28 insertions, 1 deletions

diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index 8961f08c0b..385aa3c51b 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -104,7 +104,17 @@ Rails 4.0 extracted Active Resource to its own gem. If you still need the featur
 
 ### Action Pack
 
-* Rails 4.0 introduces a new `UpgradeSignatureToEncryptionCookieStore` cookie store. This is useful for upgrading apps using the old default `CookieStore` to the new default `EncryptedCookieStore`. To use this transitional cookie store, you'll want to leave your existing `secret_token` in place, add a new `secret_key_base`, and change your `session_store` like so:
+* Rails 4.0 introduces `ActiveSupport::KeyGenerator` and uses this as a base from which to generate and verify signed cookies (among other things). Existing signed cookies generated with Rails 3.x will be transparently upgraded if you leave your existing `secret_token` in place and add the new `secret_key_base`.
+
+```ruby
+  # config/initializers/secret_token.rb
+  Myapp::Application.config.secret_token = 'existing secret token'
+  Myapp::Application.config.secret_key_base = 'new secret key base'
+```
+
+Please note that you should wait to set `secret_key_base` until you have 100% of your userbase on Rails 4.x and are reasonably sure you will not need to rollback to Rails 3.x. This is because cookies signed based on the new `secret_key_base` in Rails 4.x are not backwards compatible with Rails 3.x. You are free to leave your existing `secret_token` in place, not set the new `secret_key_base`, and ignore the deprecation warnings until you are reasonably sure that your upgrade is otherwise complete.
+
+* Rails 4.0 introduces a new `UpgradeSignatureToEncryptionCookieStore` cookie store. This is useful for upgrading apps using the old default `CookieStore` to the new default `EncryptedCookieStore` which leverages the new `ActiveSupport::KeyGenerator`. To use this transitional cookie store, you'll want to leave your existing `secret_token` in place, add a new `secret_key_base`, and change your `session_store` like so:
 
 ```ruby
   # config/initializers/session_store.rb
@@ -129,6 +139,23 @@ Rails 4.0 extracted Active Resource to its own gem. If you still need the featur
 
 * 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`:
+
+```ruby
+  get 'one' => 'test#example', as: :example
+  get 'two' => 'test#example', as: :example
+```
+
+```ruby
+  resources :examples
+  get 'clashing/:id' => 'test#example', as: :example
+```
+
+In the first case, you can simply avoid using the same name for multiple
+routes. In the second, you can use the `only` or `except` options provided by
+the `resources` method to restrict the routes created as detailed in the
+[Routing Guide](routing.html#restricting-the-routes-created).
+
 * Rails 4.0 also changed the way unicode character routes are drawn. Now you can draw unicode character routes directly. If you already draw such routes, you must change them, for example:
 
 ```ruby