This reverts commit 5d528f83.

Relates to f8c8ad56 which is also getting reverted due to failing test.

This reverts commit c321b309.

Conflicts:
	activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
	activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

Reason: failing test

  1) Error:
test_valid_column(ActiveRecord::ConnectionAdapters::SQLite3AdapterTest):
NoMethodError: undefined method `column' for
    test/cases/adapters/sqlite3/sqlite3_adapter_test.rb:29:in
`test_valid_column'

This reverts commit 8aa4603a.

Reverting the revert because I reverted the wrong thing! Fail.

This reverts commit 1fc6876b, reversing
changes made to 0268b5d8.

Reason: failing test

  1) Error:
test_valid_column(ActiveRecord::ConnectionAdapters::SQLite3AdapterTest):
NoMethodError: undefined method `column' for
    test/cases/adapters/sqlite3/sqlite3_adapter_test.rb:29:in
`test_valid_column'

Added extra comment when a migration already exists of the same name

User should know that he can overwrite the previous migration. This
comes in handy especially when generating models which were previously
created then removed.

replace regexp global in #url_for

don't cache invalid subsets when preloading hmt associations

closes #8423.

Bump rack-test dependency to 0.6.2 

Make valid_type? public

Before writing a numeric attribute value, ActiveRecord does an implicit conversion of boolean types (true => 1 and false => 0). If the numeric value being assigned is a BigDecimal, then ActiveRecord compares a BigDecimal to true and false.

This is known to be very slow in Ruby 1.9.3 (see http://www.ruby-forum.com/topic/4409452 and https://bugs.ruby-lang.org/issues/7645#change-35188).

The Ruby core team has implemented a fix for this issue that will be included in Ruby 2, but they appear to have no intention of back-porting this fix to Ruby 1.9.3. In my case, the performance impact of this issue was enormous (200% - 300% performance hit) for some of the pages in my application.

See c75b5a88 applied to 3-2-stable branch for more reasoning and a benchmark.

conversion of boolean types (true => 1 and false => 0). If the numeric value
being assigned is a BigDecimal, then ActiveRecord compares a BigDecimal to
true and false. This is known to be very slow in Ruby 1.9.3.

Don't call after_commit when creating through an association and save fails, fixes #5802

schema dumper tests now conducted by ActiveRecord::Base.Connection

Use define method instead of class_eval

fix example code in engines guide

define Active Record Store accessors in a module

Allow store accessors to be overrided like other attribute methods,
e.g.:

    class User < ActiveRecord::Base
      store :settings, accessors: [ :color, :homepage ], coder: JSON

      def color
        super || 'red'
      end
    end

Add test:all and test:all:db rake tests to speed up full test runs.

Improve img alt attribute for screen readers

fix a typo on the engine guide

Supress warning about method redifinition

In i18n gem, the following methods are defined.
- `Hash#except`
- `Hash#slice`

But if there are defined already, i18n skips these definitions.
So these definition by `active_support` are required before `require 'i18n'`.

Update to latest Unicode data.

Remove method redefined warning

In `i18n` gem, the method definition of  `Hash#deep_merge!` is skipped
when it is already defined.

- warning: method redefined; discarding old deep_merge!

Release notes at: http://www.unicode.org/versions/Unicode6.2.0/