Minitest has already been required when calling Minitest.autorun.

`Array#to` is working for negative position

Just moved class methods up in file and moved `def self.` methods into `class << self`.

This deprecation was released in 4.1.0 and can be removed for 4.2.0,
deprecation message / handling is no longer necessary.

Use if/else instead of unless/else so conditional reads better.

Use block parameter rather than `$1` during `gsub!` so `ActiveSupport::SafeBuffer` values aren't mangled.

Fixes #15064

Namely, if the mday is omitted but any other upper components are, then instead
of supplying the mday from the current time, it defaults to 1.

Current docs are wrong. Does not accept strftime inputs.

ActiveSupport::Subscriber no longer creates multiple subscribers when
you redefine a method.

* Strips leading underscores.
* Changes some unnecessary gsub!s to sub!s.
* Replaces some anchors ^, $ with \A, \z.
* Documents that human inflection rules are applied.
* Documents that words are downcased except acronyms.
* Adds an example with an acronym.
* Rewords docs.

Empty Hash or Array should not present in serialization result

    {a: []}.to_query # => ""
    {a: {}}.to_query # => ""

For more info see #14948.

After this 21dbe6f3

2.1.1 :001 > 'business'.classify
 => "Business"

2.1.1 :004 > 'calculus'.classify
 => "Calculu"
2.1.1 :005 >

Before:
  When calling String#pluralize with count=1 then it returned same
  string, but with count other than 1, returned new string.

After:
  String#pluralize always return a new string.

  => Prevent mutation of a string inadvertently.

While calling String#first or String#last with zero or a Fixnum < the
string's length returns a new string, a Fixnum >= the string's length
returns the string itself. This inconsistency can lead to inadvertent
mutation of a string.

1. Improve tests
2. Remove unnecessary constant
3. Add docs for BigDecimal#duplicable?

[ci skip]

[ci skip]

This fixes:
    1.second.eql?(1.second) #=> false

The new `eql?` requires that `other` is an `ActiveSupport::Duration`.
This requirement makes `ActiveSupport::Duration`'s behavior consistent
with other numeric types in Ruby.

    1.eql?(1.0) #=> false
    1.0.eql?(1) #=> false

    1.second.eql?(1) #=> false (was true)
    1.eql?(1.second) #=> false

    { 1 => "foo", 1.0 => "bar" }
    #=> { 1 => "foo", 1.0 => "bar" }

    { 1 => "foo", 1.second => "bar" }
    # now => { 1 => "foo", 1.second => "bar" }
    # was => { 1 => "bar" }

And though the behavior here hasn't changed, for reference:

    1 == 1.0 #=> true
    1.0 == 1 #=> true

    1 == 1.second #=> true
    1.second == 1 #=> true

It was causing error when using `with_options` passing a lambda as its
last argument.

    class User < ActiveRecord::Base
      with_options dependent: :destroy do |assoc|
        assoc.has_many :profiles, -> { where(active: true) }
      end
    end

It was happening because the `option_merger` was taking the last
argument and checking if it was a Hash. This breaks the HasMany usage,
because its last argument can be a Hash or a Proc.

As the behavior described in this test:
https://github.com/rails/rails/blob/master/activesupport/test/option_merger_test.rb#L69
the method will only accept the lambda, this way it will keep the expected behavior. See 9eaa0a34

Change to require all active_support/deprecation since that's the actual
entry point for the deprecation methods.

Make `#prepend` method modify instance in-place and return self
instead of just returning modified value. That is exactly what
`#prepend!` method was doing previously, so it's deprecated from
now on.

In particular, `.new`, `#update`, `#merge`, `#replace` all accept
objects which respond to `#to_hash`, even if those objects are not
Hashes directly.