request thread to return up the stack before the instance variable is
assigned.  Synchronize so that the ivar is assigned before the other
thread can activate.

fixes #10984

Adding documentation to the Rails initialization guide.

Omit turbolinks configuration completely on skip_javascript generator option

ActiveRecord find_in_batches should work without logger

When I set logger to nil both methods from Batches module find_in_batches or find_each should work anyway.

In 94924dc3 the internal default_scope
implementation has changed making it simpler to follow, meaning that the
old usage of with_default_scope has been removed.

With that, order_values was the same argument for both calls to
find_first_with_limit, so remove it and use the existent attribute
for the sake of clarity/simplification.

The previous implementation was necessary in order to support stuff
like:

    class Post < ActiveRecord::Base
      default_scope where(published: true)
      scope :ordered, order("created_at")
    end

If we didn't evaluate the default scope at the last possible moment
before sending the SQL to the database, it would become impossible to
do:

    Post.unscoped.ordered

This is because the default scope would already be bound up in the
"ordered" scope, and therefore wouldn't be removed by the
"Post.unscoped" part.

In 4.0, we have deprecated all "eager" forms of scopes. So now you must
write:

    class Post < ActiveRecord::Base
      default_scope { where(published: true) }
      scope :ordered, -> { order("created_at") }
    end

This prevents the default scope getting bound up inside the "ordered"
scope, which means we can now have a simpler/better/more natural
implementation of default scoping.

A knock on effect is that some things that didn't work properly now do.
For example it was previously impossible to use #except to remove a part
of the default scope, since the default scope was evaluated after the
call to #except.

Adding additional plugins to debugging guide [ci skip]

Thanks @lintzchiang. [ci skip]

For example:

    class Post < ActiveRecord::Base
      default_scope -> { where published: true }
    end

    class Comment
      belongs_to :post
    end

When calling `Comment.join(:post)`, we expect to receive only
comments on published posts, since that is the default scope for
posts.

Before this change, the default scope from `Post` was not applied,
so we'd get comments on unpublished posts.

Oops. We need to estalish/remove the connection in the setup/teardown,
else it messes with the fixtures.

Clearly nobody uses this except me. It's fast people!

Remove depreacted finders

Remove deprecation warning from AttributeMethodsMatcher

They were deprecated in 4.0, planned to remove in 4.1

Asking user to declare post resource in getting start guide

Remove deprecated attr_protected/accessible

Rails 4.0 has removed attr_protected and attr_accessible feature in favor of Strong Parameters.

Remove passing the prompt to grouped_options_for_select as an argument, because it was deprecated.

Fix documentation for grouped_collection_select

Re-remove deprecated API.

Removed "to:" from root directive and fixed typo ":to"

`root :to` is invalid syntax
`root to:` is valid, but the generated routes file omits `to:`

Fix copyright year for actionview [ci skip]

activerecord/examples/simple.rb use master branch activesupport gem

fix grammar, change 'an' to 'a' [ci skip]