It has been moved to active_record_deprecated_finders.

Use #to_a instead.

Commit 3dbedd28 added NOT NULL constraints to timestamps.
Commit fcef7289 started to revert this, but was incomplete.
With this commit, 3dbedd28 should be fully reverted and
timestamps will no longer default to NOT NULL.

For instance, running

    rails g migration CreateMediaJoinTable artists musics:uniq

will create a migration with

    create_join_table :artists, :musics do |t|
      # t.index [:artist_id, :music_id]
      t.index [:music_id, :artist_id], unique: true
    end

Introduced in 75b340d1

Fixes #867

This patch fixes quoting for ActiveSupport::Duration instances:

    # before
    >> ActiveRecord::Base.connection.quote 30.minutes
    => "'--- 1800\n...\n'"

    # after
    >> ActiveRecord::Base.connection.quote 30.minutes
    => "1800"

Also, adds a test for type casting ActiveSupport::Duration instances.

Related to #1119.

Examples:

    add_reference :products, :supplier, polymorphic: true, index: true
    remove_reference :products, :user

`add_belongs_to` and `remove_belongs_to` are
acceptable.

Also fix failures in check options for nil

Get rid of ActiveModel::Configuration, make better use of
ActiveSupport::Concern + class_attribute, etc.

The core of this fix is a threadsafe, fair Queue class.  It is
very similar to Queue in stdlib except that it supports waiting
with a timeout.

The issue this solves is that if several threads are contending for
database connections, an unfair queue makes is possible that a thread
will timeout even while other threads successfully acquire and release
connections.  A fair queue means the thread that has been waiting the
longest will get the next available connection.

This includes a few test fixes to avoid test ordering issues that
cropped up during development of this patch.

This reverts commit fa6d921e.

Reason: Not a fan of such massive changes. We usually close such changes
if made to Rails master as a pull request. Following the same principle
here and reverting.

[ci skip]

An AR ConnectionSpec `wait_timeout` is pre-patch used for three
different things:

* mysql2 uses it for MySQL's own wait_timeout (how long MySQL
  should allow an idle connection before closing it), and
  defaults to 2592000 seconds.
* ConnectionPool uses it for "number of seconds to block and
  wait for a connection before giving up and raising a timeout error",
  default 5 seconds.
* ConnectionPool uses it for the Reaper, for deciding if a 'dead'
  connection can be reaped. Default 5 seconds.

Previously, if you want to change these from defaults, you need
to change them all together. This is problematic _especially_
for the mysql2/ConnectionPool conflict, you will generally _not_
want them to be the same, as evidenced by their wildly different
defaults. This has caused real problems for people #6441 #2894

But as long as we're changing this, forcing renaming the
ConnectionPool key to be more specific, it made sense
to seperate the two ConnectionPool uses too -- these two
types of ConnectionPool timeouts ought to be able to be
changed independently, you won't neccesarily want them
to be the same, even though the defaults are (currently)
the same.

This reverts commit d2901f0f, reversing
changes made to 525839fd.

Conflicts:
	activerecord/test/cases/connection_pool_test.rb

Reason: This change broke the build (http://travis-ci.org/#!/rails/rails/builds/1391490)
and we don't have any solution until now. I asked the author to try to
fix it and open a new pull request.

For future reference, this is the regex I used: ^\s*#\s*\n(?!\s*#). Replace
with the first match, and voilà! Note that the regex matches a little bit too
much, so you probably want to `git add -i .` and go through every single diff
to check if it actually should be changed.

This reverts commit 23a98ffb.

[ci skip]