Bring abstract_controller up to date with rails/master

Resolved all the conflicts since 2.3.0 -> HEAD. Following is a list
of commits that could not be applied cleanly or are obviated with the
abstract_controller refactor. They all need to be revisited to ensure
that fixes made in 2.3 do not reappear in 3.0:

2259ecf368e6a6715966f69216e3ee86bf1a82a7
AR not available
  * This will be reimplemented with ActionORM or equivalent

06182ea02e92afad579998aa80144588e8865ac3
implicitly rendering a js response should not use the default layout
[#1844 state:resolved]
  * This will be handled generically

893e9eb99504705419ad6edac14d00e71cef5f12
Improve view rendering performance in development mode and reinstate
template recompiling in production [#1909 state:resolved]
  * We will need to reimplement rails-dev-boost on top of the refactor;
    the changes here are very implementation specific and cannot be
    cleanly applied. The following commits are implicated:

      199e750d46c04970b5e7684998d09405648ecbd4
      3942cb406e1d5db0ac00e03153809cc8dc4cc4db
      f8ea9f85d4f1e3e6f3b5d895bef6b013aa4b0690
      e3b166aab37ddc2fbab030b146eb61713b91bf55
      ae9f258e03c9fd5088da12c1c6cd216cc89a01f7
      44423126c6f6133a1d9cf1d0832b527e8711d40f

0cb020b4d6d838025859bd60fb8151c8e21b8e84
workaround for picking layouts based on wrong view_paths
[#1974 state:resolved]
  * The specifics of this commit no longer apply. Since it is a two-line
    commit, we will reimplement this change.

8c5cc66a831aadb159f3daaffa4208064c30af0e
make action_controller/layouts pick templates from the current instance's
view_paths instead of the class view_paths [#1974 state:resolved]
  * This does not apply at all. It should be trivial to apply the feature
    to the reimplemented ActionController::Base.

87e8b162463f13bd50d27398f020769460a770e3
fix HTML fallback for explicit templates [#2052 state:resolved]
  * There were a number of patches related to this that simply compounded
    each other. Basically none of them apply cleanly, and the underlying
    issue needs to be revisited. After discussing the underlying problem
    with Koz, we will defer these fixes for further discussion.

1 files changed, 0 insertions, 159 deletions

diff --git a/railties/doc/guides/source/migrations/writing_a_migration.txt b/railties/doc/guides/source/migrations/writing_a_migration.txt
deleted file mode 100644
index 2a2b6217d8..0000000000
--- a/railties/doc/guides/source/migrations/writing_a_migration.txt
+++ /dev/null
@@ -1,159 +0,0 @@
-== Writing a Migration ==
-
-Once you have created your migration using one of the generators it's time to get to work!
-
-=== Creating a table ===
-
-`create_table` will be one of your workhorses. A typical use would be
-
-[source, ruby]
----------------------
-create_table :products do |t|
-  t.string :name
-end
----------------------
-which creates a `products` table with a column called `name` (and as discussed below, an implicit `id` column).
-
-The object yielded to the block allows you create columns on the table. There are two ways of doing this. The first looks like
-
-[source, ruby]
----------------------
-create_table :products do |t|
-  t.column :name, :string, :null => false
-end
----------------------
-
-the second form, the so called "sexy" migrations, drops the somewhat redundant column method. Instead, the `string`, `integer` etc. methods create a column of that type. Subsequent parameters are identical.
-
-[source, ruby]
----------------------
-create_table :products do |t|
-  t.string :name, :null => false
-end
----------------------
-
-By default `create_table` will create a primary key called `id`. You can change the name of the primary key with the `:primary_key` option (don't forget to update the corresponding model) or if you don't want a primary key at all (for example for a HABTM join table) you can pass `:id => false`. If you need to pass database specific options you can place an sql fragment in the `:options` option. For example
-
-[source, ruby]
----------------------
-create_table :products, :options => "ENGINE=BLACKHOLE" do |t|
-  t.string :name, :null => false
-end
----------------------
-Will append `ENGINE=BLACKHOLE` to the sql used to create the table (when using MySQL the default is "ENGINE=InnoDB").
-
-The types Active Record supports are `:primary_key`, `:string`, `:text`, `:integer`, `:float`, `:decimal`, `:datetime`, `:timestamp`, `:time`, `:date`, `:binary`, `:boolean`.
-
-These will be mapped onto an appropriate underlying database type, for example with MySQL `:string` is mapped to `VARCHAR(255)`. You can create columns of 
-types not supported by Active Record when using the non sexy syntax, for example
-
-[source, ruby]
----------------------
-create_table :products do |t|
-  t.column :name, 'polygon', :null => false
-end
----------------------
-This may however hinder portability to other databases.
-
-=== Changing tables ===
-
-`create_table`'s close cousin is `change_table`. Used for changing existing tables, it is used in a similar fashion to `create_table` but the object yielded to the block knows more tricks. For example
-
-[source, ruby]
----------------------
-change_table :products do |t|
-  t.remove :description, :name
-  t.string :part_number
-  t.index :part_number
-  t.rename :upccode, :upc_code
-end
----------------------
-removes the `description` column, creates a `part_number` column and adds an index on it. Finally it renames the `upccode` column.   This is the same as doing
-
-[source, ruby]
----------------------
-remove_column :products, :description
-remove_column :products, :name
-add_column :products, :part_number, :string
-add_index :products, :part_number
-rename_column :products, :upccode, :upc_code
----------------------
-
-You don't have to keep repeating the table name and it groups all the statements related to modifying one particular table. The individual transformation names are also shorter, for example `remove_column` becomes just `remove` and `add_index` becomes just `index`.
-
-=== Special helpers ===
-
-Active Record provides some shortcuts for common functionality. It is for example very common to add both the `created_at` and `updated_at` columns and so there is a method that does exactly that:
-
-[source, ruby]
----------------------
-create_table :products do |t|
-  t.timestamps
-end
----------------------
-will create a new products table with those two columns whereas
-
-[source, ruby]
----------------------
-change_table :products do |t|
-  t.timestamps
-end
----------------------
-adds those columns to an existing table.
-
-The other helper is called `references` (also available as `belongs_to`). In its simplest form it just adds some readability
-
-[source, ruby]
----------------------
-create_table :products do |t|
-  t.references :category
-end
----------------------
-
-will create a `category_id` column of the appropriate type. Note that you pass the model name, not the column name. Active Record adds the `_id` for you. If you have polymorphic belongs_to associations then `references` will add both of the columns required:
-
-[source, ruby]
----------------------
-create_table :products do |t|
-  t.references :attachment, :polymorphic => {:default => 'Photo'}
-end
----------------------
-will add an `attachment_id` column and a string `attachment_type` column with a default value of 'Photo'.
-
-NOTE: The `references` helper does not actually create foreign key constraints for you. You will need to use `execute` for that or a plugin that adds <<foreign_key,foreign key support>>.
-
-If the helpers provided by Active Record aren't enough you can use the `execute` function to execute arbitrary SQL.
-
-For more details and examples of individual methods check the API documentation, in particular the documentation for http://api.rubyonrails.com/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html[ActiveRecord::ConnectionAdapters::SchemaStatements] (which provides the methods available in the `up` and `down` methods),  http://api.rubyonrails.com/classes/ActiveRecord/ConnectionAdapters/TableDefinition.html[ActiveRecord::ConnectionAdapters::TableDefinition] (which provides the methods available on the object yielded by `create_table`) and http://api.rubyonrails.com/classes/ActiveRecord/ConnectionAdapters/Table.html[ActiveRecord::ConnectionAdapters::Table] (which provides the methods available on the object yielded by `change_table`).
-
-=== Writing your down method ===
-
-The `down` method of your migration should revert the transformations done by the `up` method. In other words the database should be unchanged if you do an `up` followed by a `down`. For example if you create a table in the up you should drop it in the `down` method. It is wise to do things in precisely the reverse order to in the `up` method. For example
-
-[source, ruby]
----------------------
-class ExampleMigration < ActiveRecord::Migration
-
-  def self.up
-    create_table :products do |t|
-      t.references :category
-    end
-    #add a foreign key
-    execute "ALTER TABLE products ADD CONSTRAINT fk_products_categories FOREIGN KEY (category_id) REFERENCES categories(id)"
-    
-    add_column :users, :home_page_url, :string
-    
-    rename_column :users, :email, :email_address
-  end
-  
-  def self.down
-    rename_column :users, :email_address, :email
-    remove_column :users, :home_page_url
-    execute "ALTER TABLE products DROP FOREIGN KEY fk_products_categories"
-    drop_table :products
-  end
-end
----------------------
-Sometimes your migration will do something which is just plain irreversible, for example it might destroy some data. In cases like those when you can't reverse the migration you can raise IrreversibleMigration from your `down` method. If someone tries to revert your migration an error message will be
-displayed saying that it can't be done.
-