Typo in AR CHANGELOG [ci skip]
Merge pull request #15353 from sgrif/sg-mysql-condition

Remove unnecessary branch from quoting in Mysql
Merge pull request #15301 from zzak/issue_15212

Skip if the association was already loaded.
Add test case for b13d260
Move test to the proper file

All preload tests are in the eager_test file
Fix syntax error from 5eae77c
Remove `require 'active_support'` from individual modules

Let users require `active_support` before loading any ActiveSupport modules
http://guides.rubyonrails.org/active_support_core_extensions.html
Fix redefine a has_and_belongs_to_many inside inherited class

After ad7b5efb55bcc2e0ccd3e7f22a81e984df8676d1, which changed how
has_an_belongs_to_many used to work, we start raising an error when
redefining the same has_an_belongs_to_many association. This commits fix
that regression.

[Fixes #14983]
Merge pull request #15356 from deeeki/activesupport_loading

Remove `require 'active_support'` from individual modules
Merge pull request #15327 from alexbel/replace_double_quotes_with_single_quotes

Replace double quotes with single quotes while adding an entry into Gemfile
[ci skip] Fix Compiler's Github link
Deprecate decimal columns being automatically treated as integers

With ActiveRecord::Properties, we now have a reasonable path for users
to continue to keep this behavior if they want it. This is an edge case
that has added a lot of complexity to the code base.
Merge pull request #15359 from kuldeepaggarwal/f-remove-unwanted_to_sym

remove unwanted `to_sym` call.
Merge pull request #15358 from arthurnn/redefine_habtm_fix

Fix redefine a has_and_belongs_to_many inside inherited class
Speed-up TimeWithZone to String conversion

I've noticed that `String(model.created_at)` is performing poorly in comparision
with other fields. The source of the problem is a way `Kernel#String` works: it first
tries to call `to_str` (which causes `NoMethodError` in `method_missing`) and then calls `to_s`.

Performance tests:

    tz = Time.zone.now

    Benchmark.ips do |x|
      x.report { String(tz) }
    end

Without this code:

    Calculating -------------------------------------
                               572 i/100ms
    -------------------------------------------------
                            10177.7 (±18.2%) i/s -      48620 in   5.000325s

With this code:

    Calculating -------------------------------------
                              1518 i/100ms
    -------------------------------------------------
                           138984.2 (±10.1%) i/s -     677028 in   4.974897s
rake railties:install:migrations respects the order of railties

This PR fixes #8930 and some stuff from #8985
Merge pull request #15295 from sgrif/sg-deprecate-decimals

Deprecate decimal columns being automatically treated as integers
Merge pull request #14834 from al2o3cr/issue14155

Correctly alias table names when joining more than once
Require active_support at the railties

Railties need to be used without having to require any dependecy first.
Merge pull request #15321 from tgxworld/only_find_routes_as_heads_for_head_request

Call get_routes_as_head only on HEAD requests.