Create with_env helper for tests.

Return a null object from `AttributeSet#[]`

Move `attributes` to the `AttributeSet` object.

Add missing test cases for `attribute_method?`

Use with_parse_json_times helper in tests.

Avoid hardcoded magic number in test teardown.

[ci skip] Add Tip for change_column_null and change_column_default in guides

Make dependencies.rb add a name to NameError

The :singleton-method: directive is printed in the docs.
This directive is not necessary as the method is documentable just fine.

Add to guides app and helper objects on command line

Fix state leak.

Remove extra list item element in engine guide

Cleaning up the list items that detail what an engines `--full` option
generates. Joining a multiline multi list item into a multiline single
list item.

[ci skip]

Don't save through records twice

Conflicts:
	activerecord/CHANGELOG.md
	activerecord/test/cases/associations/has_many_through_associations_test.rb

ErrorsController shouldn't inherit ApplicationController, but ActionController

Always update counter caches in memory when adding records

Inheriting `ApplicationController` often causes an issue as it always
has before/after actions. It should encourage to use `ActionController::Base` instead.

[ci skip]

Don't use `Column` for type casting in Relation calculations

Don't use column object when calculating type cast defaults

Don't use column object for type casting in `quoting`

Don't rely on the column for type casting reflections

Further simplify `changed?` conditional for numeric types

remove unnecessary gsub for space in ActionView::Helpers#debug

Introduce an object to aid in creation and management of `@attributes`

Mostly delegation to start, but we can start moving a lot of behavior in
bulk to this object.

[ci skip]

Create custom errors page on ActionController guides

highlight/except support for regular expressions and blocks.

The helper will yield each matched word, and you can use this instead of the
':highlighter' option for more complex replacing logic:

  highlight('My email is me@work.com', EMAIL_REGEXP) { |m| mail_to(m) }
  # => 'My email is <a href="mailto:me@work.com">me@work.com</a>'