Fixed typo in migrations guide [ci skip]

Product model name was pluralized in example in migrations guide.
[ci skip]

addresses "ArgumentError: comparison of VerySpecialComment with SpecialComment failed" in ActiveRecord::DelegationRelationTest#test_#sort!_delegation_is_deprecated

Without this, some tests here were not actually testing anything.

Fixes problem with replacing has_one association record with itself

[ci skip]

autoload ChangeColumnDefinition (Fixes #12835)

Fix missing line and shadow on static error pages [ci skip]

Speed up Array#split when block is passed

Ruby 2.0.0p247
Rehearsal ---------------------------------------
old  10.670000   0.150000  10.820000 ( 10.822651)
new   8.520000   0.050000   8.570000 (  8.571825)
----------------------------- total: 19.390000sec

          user     system      total        real
old  10.620000   0.170000  10.790000 ( 10.790409)
new   8.570000   0.110000   8.680000 (  8.686051)

Array#in_groups: documentation updated [ci skip]

Array#split preserving the calling array

Remove @order attribute from collector

Ruby 1.8 legacy. Since 1.9 hash preserves insertion order. No need for additional array to achieve this

Improve Errors when Controller Name or Action isn't specfied

Add test for ActiveRecord::Relation YAML serialization, for #5303 issue

Update tzinfo

Include the tzinfo-data in the generated Gemfile on Windows.

instead of 'rake test' as shortcut, use 'rake'.

Closes #12780 [ci skip]

This is the only argument that changes over the method calls so it is
better to it be the first one

clarified missleading message

(No database connection) sounds not be
able to connect database.

see more #12804

The generators entry point file is rails/generators so we need to make
sure uers will be able to use the generators when requiring that file.

Fixes #12802

This is a follow up to: 97f0d9a0
This change is also related to: df0edafa

This will make the conditional and to code clear