This is a follow up to #15602 which rendered the guides in a weird state:

  >  You can also specify some options just after the field type between curly
     braces. You can use the following modifiers:

  >  `null`         Allows or disallows `NULL` values in the column.

  >  NOTE: `null` and `default` cannot be specified via command line.

The modifiers are now moved into a separate section. The generator
simply referes to that section.

Related to #15583.

/cc @JuanitoFatas

Conflicts:
	guides/source/migrations.md

ActiveRecord::FinderMethods.find doesn't pass proc parameter to array

Manual merge of #15584.

Closes #15584.

Conflicts:
	activerecord/CHANGELOG.md
	activerecord/test/cases/finder_test.rb

[ci skip] Add note about type modifiers that cannot be specified in command line.

This reverts commit dd3ea171 and add a
regression test.

Fixes #15418

Conflicts:
	activerecord/CHANGELOG.md

Integration tests are inside protected_attributes test suite.

Fixes #15496
Fixes rails/protected_attributes#35

Mail 2.6.1 silences excessive warnings; remove Gemfile hack
Conflicts:
	Gemfile

Before this patch, using `ActiveRecord::Base.primary_key_prefix_type`
with `:table_name_with_underscore` would change the `SchemaMigration` model
to have a primary key. This resulted in broken queries for PG because it tried
to return the inserted PK (which does not exist).

Closes #15051.
Closes #15419.

Unlike the outer `rescue`, this one is much more precise about what we
want to handle: a connection failure (`Dalli::RingError`) is not
relevant to what we're testing here. But other Dalli errors may well be
indicating an actual problem.

The migration numbers were normalized different ways. This left
the task output in an inconsistent state.

Closes #15538.

Conflicts:
	activerecord/CHANGELOG.md

Closes #15541.

Conflicts:
	guides/source/active_record_querying.md

2.6 currently has many warnings, which are failing the Travis build.

Conflicts:
	Gemfile

Fix regression on eager loading association based on SQL query rather than existing column.

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

Relax mail gem constraint from ~> 2.5.4 to ~> 2.5

Avoid namespacing routes inside engines
Conflicts:
	railties/CHANGELOG.md

Closes #15376

Fix AS::NumberHelper results with rationals
Conflicts:
	activesupport/CHANGELOG.md

[ci skip]

We only introduce new deprecations at Minor releases.

Fixed #columns_for_distinct of postgresql adapter

Conflicts:
	activerecord/CHANGELOG.md

Conflicts:
	activerecord/CHANGELOG.md

The solution presented in this patch is not efficient. We should replace it
in the near future. The following needs to be worked out:
  * Is `@attributes` storing the Ruby or SQL representation?
  * `cacheable_column?` is broken but `hstore` and `json` rely on that behavior

Closes #15369.

Option discovered by @zackperdue in #14741, implemented in #5581.

Fix documentation

This reverts commit 38cf00e5.

Conflicts:
	railties/CHANGELOG.md

Correctly alias table names when joining more than once

rake railties:install:migrations respects the order of railties

Fix redefine a has_and_belongs_to_many inside inherited class
Conflicts:
	activerecord/CHANGELOG.md

All preload tests are in the eager_test file

Skip if the association was already loaded.

Now the internal reflections will hold a reference to its public
representation, so when the outside world calls `Account.reflection` we
can build a list of public reflections.

Conflicts:
	activerecord/lib/active_record/associations.rb
	activerecord/lib/active_record/counter_cache.rb
	activerecord/lib/active_record/reflection.rb

This is not a security issue since this page is not present in
production and user have to type something in the field but is better to
escape the input.

Conflicts:
	guides/CHANGELOG.md
	guides/code/getting_started/Gemfile
	guides/source/debugging_rails_applications.md

I don't know when this changed, checked back up to 3.2 and integration
tests instantiate fixtures just fine.

avoid using alias in generators

Fixes URL generation with trailing_slash: true

Conflicts:
	actionpack/lib/action_dispatch/http/url.rb

Conflicts:
	actionpack/CHANGELOG.md
	actionpack/lib/action_dispatch/http/url.rb