Improve a code style recommendation following Rubocop instructions https://codeclimate.com/github/rails/rails/issues

Remove `supports_disable_referential_integrity?`

`supports_disable_referential_integrity?` used to handle
if PostgreSQL database supports
`ALTER TABLE <table name> DISABLE/ENABLE TRIGGER` statements.
Refer https://github.com/rails/rails/commit/9a947af0e79cfb8692eb7e5ae94c1b8c40756f49

These statements have been documented since 8.1.

https://www.postgresql.org/docs/8.1/static/sql-altertable.html
> DISABLE/ENABLE TRIGGER

Now Rails supports PostgreSQL 9.1 or higher only.
No need to handle `supports_disable_referential_integrity?` anymore.
Also, this method does not exist in any other adapters including AbstractAdapter.

Performance improvements for acts_like? method

Fix #to_json for IO objects, fixes #26132

activesupport/lib/active_support/core_ext/object/acts_like.rb
acts_like?

Add a case statement to use direct symbols instead of string
interpolation for the three scenarios I found in the Rails codebase:
time, date, and string.

For time/date/string, this change prevents two string allocations for
each time the method is called and speeds up the method by ~2.7x. For
other arguments, there is no memory difference and performance
difference is within margin of error.

begin
  require "bundler/inline"
rescue LoadError => e
  $stderr.puts "Bundler version 1.10 or later is required. Please update
                your Bundler"
  raise e
end

gemfile(true) do
  source "https://rubygems.org"

  gem "rails", github: "rails/rails"
  gem "arel", github: "rails/arel"
  gem "benchmark-ips"
end

def allocate_count
  GC.disable
  before = ObjectSpace.count_objects
  yield
  after = ObjectSpace.count_objects
  after.each { |k,v| after[k] = v - before[k] }
  after[:T_HASH] -= 1 # probe effect - we created the before hash.
  GC.enable
  result = after.reject { |k,v| v == 0 }
  GC.start
  result
end

class Object
  def fast_acts_like?(duck)
    case duck
    when :time
      respond_to? :acts_like_time?
    when :date
      respond_to? :acts_like_date?
    when :string
      respond_to? :acts_like_string?
    else
      respond_to? :"acts_like_#{duck}?"
    end
  end
end

puts
puts " acts_like? ".center(80, '=')
puts

obj = ''.freeze

%i(time date string super_hacka).each do |type|
  puts " #{type} ".center(80, '=')

  puts " Memory Usage ".center(80, "=")
  puts

  puts "value.acts_like?"
  puts allocate_count { 1000.times { obj.acts_like?(type) } }

  puts "value.fast_acts_like?"
  puts allocate_count { 1000.times { obj.fast_acts_like?(type) } }

  puts
  puts " Benchmark.ips ".center(80, "=")
  puts

  Benchmark.ips do |x|
    x.report("acts_like?")      { obj.acts_like?(type) }
    x.report("fast_acts_like?") { obj.fast_acts_like?(type) }
    x.compare!
  end
end

================================== acts_like? ==================================

===================================== time =====================================
================================= Memory Usage =================================

value.acts_like?
{:FREE=>-1983, :T_STRING=>2052, :T_IMEMO=>1}
value.fast_acts_like?
{:FREE=>-1}

================================ Benchmark.ips =================================

Warming up --------------------------------------
          acts_like?   104.281k i/100ms
     fast_acts_like?   155.523k i/100ms
Calculating -------------------------------------
          acts_like?      1.688M (±10.7%) i/s -      8.342M in   5.003804s
     fast_acts_like?      4.596M (±12.1%) i/s -     22.551M in   5.000124s

Comparison:
     fast_acts_like?:  4596162.4 i/s
          acts_like?:  1688163.8 i/s - 2.72x  slower

===================================== date =====================================
================================= Memory Usage =================================

value.acts_like?
{:FREE=>-2001, :T_STRING=>2000}
value.fast_acts_like?
{:FREE=>-1}

================================ Benchmark.ips =================================

Warming up --------------------------------------
          acts_like?    85.372k i/100ms
     fast_acts_like?   166.097k i/100ms
Calculating -------------------------------------
          acts_like?      1.720M (± 8.3%) i/s -      8.537M in   5.001003s
     fast_acts_like?      4.695M (±10.1%) i/s -     23.254M in   5.010734s

Comparison:
     fast_acts_like?:  4695493.1 i/s
          acts_like?:  1719637.9 i/s - 2.73x  slower

==================================== string ====================================
================================= Memory Usage =================================

value.acts_like?
{:FREE=>-2001, :T_STRING=>2000}
value.fast_acts_like?
{:FREE=>-1}

================================ Benchmark.ips =================================

Warming up --------------------------------------
          acts_like?   100.221k i/100ms
     fast_acts_like?   182.841k i/100ms
Calculating -------------------------------------
          acts_like?      1.706M (± 7.3%) i/s -      8.519M in   5.022331s
     fast_acts_like?      3.968M (±22.8%) i/s -     18.650M in   5.006762s

Comparison:
     fast_acts_like?:  3967972.9 i/s
          acts_like?:  1705773.7 i/s - 2.33x  slower

================================= super_hacka ==================================
================================= Memory Usage =================================

value.acts_like?
{:FREE=>-2004, :T_STRING=>2002, :T_SYMBOL=>1}
value.fast_acts_like?
{:FREE=>-2003, :T_STRING=>2001, :T_SYMBOL=>1}

================================ Benchmark.ips =================================

Warming up --------------------------------------
          acts_like?   100.344k i/100ms
     fast_acts_like?   101.690k i/100ms
Calculating -------------------------------------
          acts_like?      1.617M (± 7.5%) i/s -      8.128M in   5.055285s
     fast_acts_like?      1.534M (±10.1%) i/s -      7.627M in   5.031052s

Comparison:
          acts_like?:  1617390.7 i/s
     fast_acts_like?:  1533897.3 i/s - same-ish: difference falls within error

specify minimum capybara version for system tests

Start bringing attributes API to AM

Remove mention about Evented Redis [ci skip] 

Evented Redis is removed from Rails.
See #30945

Upgraded rails applications may have a Gemfile without a new enough
capybara to run system tests. Setting a version here gives the user a
more direct error message than they get otherwise.  Resolves #30952

Remove deprecations

Remove CHANGELOG entry for the change that was backported to 5-1-stable [ci skip]

Remove deprecated methods `initialize_schema_migrations_table` and `initialize_internal_metadata_table`

- It was backported in
  https://github.com/rails/rails/commit/0eae8dd4b859c109919e5da0d6e74ffc6dc8a258
  and is present in Rails 5.1.3

It should be shared the count of alias tracking in both INNER/LEFT JOINs
to avoid duplicate aliases.

Fixes #30504.
Closes #30410.

Currently we have no test for alias tracking with string joins. I've add
test case for that to catch a future regression.

Since `MocktailDesigner` inherits `DrinkDesigner` and can not be used
alone.