http links will be redirected to the https version, but still better to
just directly link to the https version.

* In 5.2 release note, added [securing rails app guide](http://edgeguides.rubyonrails.org/security.html#custom-credentials) link to [credentials section](http://edgeguides.rubyonrails.org/5_2_release_notes.html#credentials).

- Add mention about "nonce".

Related to https://github.com/rails/rails/pull/32222#issuecomment-372268157

- Remove
  ```
  *   Namespace error pages' CSS selectors to stop the styles from bleeding
      into other pages when using Turbolinks.
      ([Pull Request](https://github.com/rails/rails/pull/28814))
  ```
  since it was backported to
  `5-1-stable` by 50d5baf7
  and
  `5-0-stable` by d1c4a39e.

- Remove
  ```
  *   Allow irb options to be passed from `rails console` command.
      ([Pull Request](https://github.com/rails/rails/pull/29010))
  ```
  since it was backported to
  `5-1-stable` by e91b4834.

- Remove
  ```
  *   Load environment file in `dbconsole` command.
      ([Pull Request](https://github.com/rails/rails/pull/29725))
  ```
  since it was backported to
  `5-1-stable` by 7f934287.

- Remove
  ```
  *   Gemfile for new apps: upgrade redis-rb from ~> 3.0 to 4.0.
      ([Pull Request](https://github.com/rails/rails/pull/30748))
  ```
  since it was backported to
  `5-1-stable` by 37895311.

- Remove
  ```
  *   Fix minitest rails plugin.
      The custom reporters are added only if needed.
      This will fix conflicts with others plugins.
      ([Commit](https://github.com/rails/rails/commit/ac99916fcf7bf27bb1519d4f7387c6b4c5f0463d))
  ```
  since it was backported to
  `5-1-stable` by caa76956.

- Remove
  ```
  *   Add support for compatibility with redis-rb gem for 4.0 version.
      ([Pull Request](https://github.com/rails/rails/pull/30748))
  ```
  since it was backported to
  `5-1-stable` by 37895311.

- Remove
  ```
  *   Add `action_controller_api` and `action_controller_base` load hooks to be
      called in `ActiveSupport.on_load`.
      ([Pull Request](https://github.com/rails/rails/pull/28402))
  ```
  since it was backported to
  `5-1-stable` by b9a5fd70.

- Remove
  ```
  *   `driven_by` now registers poltergeist and capybara-webkit.
      ([Pull Request](https://github.com/rails/rails/pull/29315))
  ```
  since it was backported to
  `5-1-stable` by c5dd4511.

- Remove
  ```
  *   Fallback `ActionController::Parameters#to_s` to `Hash#to_s`.
      ([Pull Request](https://github.com/rails/rails/pull/29630))
  ```
  since it was backported to
  `5-1-stable` by c1014e43
  and
  `5-0-stable` by 0e71fc30.

- Remove
  ```
  *   Make `take_failed_screenshot` work within engine.
      ([Pull Request](https://github.com/rails/rails/pull/30421))
  ```
  since it was backported to
  `5-1-stable` by 595a2310.

- Remove
  ```
  *   Fix optimized url helpers when using relative url root.
      ([Pull Request](https://github.com/rails/rails/pull/31261))
  ```
  since it was backported to
  `5-1-stable` by e9b77953.

- Remove
  ```
  *   Update `distance_of_time_in_words` helper to display better error messages
      for bad input.
      ([Pull Request](https://github.com/rails/rails/pull/20701))
  ```
  since it was backported to
  `5-1-stable` by 2c97fbf6.

- Remove
  ```
  *   Generate field ids in `collection_check_boxes` and
      `collection_radio_buttons`.
      ([Pull Request](https://github.com/rails/rails/pull/29412))
  ```
  since it was backported to
  `5-1-stable` by 2d8c10a7.

- Remove
  ```
  *   Fix issues with scopes and engine on `current_page?` method.
      ([Pull Request](https://github.com/rails/rails/pull/29503))
  ```
  since it was backported to
  `5-1-stable` by 2135daf0.

- Remove
  ```
  *   Bring back proc with arity of 1 in `ActionMailer::Base.default` proc
      since it was supported in Rails 5.0 but not deprecated.
      ([Pull Request](https://github.com/rails/rails/pull/30391))
  ```
  since it was backported to
  `5-1-stable` by b2bedb14.

- Remove
  ```
  *   Add type caster to `RuntimeReflection#alias_name`.
      ([Pull Request](https://github.com/rails/rails/pull/28961))
  ```
  since it was backported to
  `5-1-stable` by f644e7a6.

- Remove
  ```
  *   Loading model schema from database is now thread-safe.
      ([Pull Request](https://github.com/rails/rails/pull/29216))
  ```
  since it was backported to
  `5-1-stable` by 02926cff.
  and
  `5-0-stable` by 84bcfe5a

- Remove
  ```
  *   Fix destroying existing object does not work well when optimistic locking
      enabled and `locking_column` is null in the database.
      ([Pull Request](https://github.com/rails/rails/pull/28926))
  ```
  since it was backported to
  `5-1-stable` by e498052c.

- Remove
  ```
  *   `ActiveRecord::Persistence#touch` does not work well
      when optimistic locking enabled and `locking_column`,
      without default value, is null in the database.
      ([Pull Request](https://github.com/rails/rails/pull/28914))
  ```
  since it was backported to
  `5-1-stable` by 1e2f63db.

- Remove
  ```
  *   Previously, when building records using a `has_many :through` association,
      if the child records were deleted before the parent was saved,
      they would still be persisted. Now, if child records are deleted
      before the parent is saved on a `has_many :through` association,
      the child records will not be persisted.
      ([Pull Request](https://github.com/rails/rails/pull/29593))
  ```
  since it was backported to
  `5-1-stable` by a22c39e9.

- Remove
  ```
  *   Query cache was unavailable when entering the `ActiveRecord::Base.cache`
      block without being connected.
      ([Pull Request](https://github.com/rails/rails/pull/29609))
  ```
  since it was backported to
  `5-1-stable` by fd6c8cdf
  and
  `5-0-stable` by 9f2532bb.

- Remove
  ```
  *   `Relation#joins` is no longer affected by the target model's
      `current_scope`, with the exception of `unscoped`.
      ([Commit](https://github.com/rails/rails/commit/5c71000d086cc42516934415b79380c2224e1614))
  ```
  since it was backported to
  `5-1-stable` by 3630d635.

- Remove
  ```
  *   Fix `unscoped(where: [columns])` removing the wrong bind values.
      ([Pull Request](https://github.com/rails/rails/pull/29780))
  ```
  since it was backported to
  `5-1-stable` by d378fcb2.

- Remove
  ```
  *   When a `has_one` association is destroyed by `dependent: destroy`,
      `destroyed_by_association` will now be set to the reflection, matching the
      behaviour of `has_many` associations.
      ([Pull Request](https://github.com/rails/rails/pull/29855))
  ```
  since it was backported to
  `5-1-stable` by 8254a8be.

- Remove
  ```
  *   Fix `COUNT(DISTINCT ...)` with `ORDER BY` and `LIMIT`
      to keep the existing select list.
      ([Pull Request](https://github.com/rails/rails/pull/29848))
  ```
  since it was backported to
  `5-1-stable` by 0e8d4edd.

- Remove
  ```
  *   Ensure `sum` honors `distinct` on `has_many :through` associations.
      ([Commit](https://github.com/rails/rails/commit/566f1fd068711dfe557bef63406f8dd6d41d473d))
  ```
  since it was backported to
  `5-1-stable` by c0a1dc25.

- Remove
  ```
  *   Fix `COUNT(DISTINCT ...)` for `GROUP BY` with `ORDER BY` and `LIMIT`.
      ([Commit](https://github.com/rails/rails/commit/5668dc6b1863ef43be8f8ef0fb1d5db913085fb3))
  ```
  since it was backported to
  `5-1-stable` by 87ca68e7.

- Remove
  ```
  *   MySQL: Don't lose `auto_increment: true` in the `db/schema.rb`.
      ([Commit](https://github.com/rails/rails/commit/9493d4553569118b2a85da84fd3a8ba2b5b2de76))
  ```
  since it was backported to
  `5-1-stable` by 8b6e694e.

- Remove
  ```
  *   Fix longer sequence name detection for serial columns.
      ([Pull Request](https://github.com/rails/rails/pull/28339))
  ```
  since it was backported to
  `5-1-stable` by af9c1707
  and
  `5-0-stable` by 7025b1d8.

- Remove
  ```
  *   Fix `bin/rails db:setup` and `bin/rails db:test:prepare` create wrong
      ar_internal_metadata's data for a test database.
      ([Pull Request](https://github.com/rails/rails/pull/30579))
  ```
  since it was backported to
  `5-1-stable` by bb67b5f2
  and
  `5-0-stable` by 60437e6d.

- Remove
  ```
  *   Fix conflicts `counter_cache` with `touch: true` by optimistic locking.
      ([Pull Request](https://github.com/rails/rails/pull/31405))
  ```
  since it was backported to
  `5-1-stable` by 5236ddaf.

- Remove
  ```
  *   Fix `count(:all)` to correctly work `distinct` with custom SELECT list.
      ([Commit](https://github.com/rails/rails/commit/c6cd9a59f200863ccfe8ad1d9c5a8876c39b9c5c))
  ```
  since it was backported to
  `5-1-stable` by 6beb4de7.

- Remove
  ```
  *   Fix to invoke callbacks when using `update_attribute`.
      ([Commit](https://github.com/rails/rails/commit/732aa34b6e6459ad66a3d3ad107cfff75cc45160))
  ```
  since it was backported to
  `5-1-stable` by 6346683b.

- Remove
  ```
  *   Use `count(:all)` in `HasManyAssociation#count_records` to prevent invalid
      SQL queries for association counting.
      ([Pull Request](https://github.com/rails/rails/pull/27561))
  ```
  since it was backported to
  `5-1-stable` by eef3c89e.

- Remove
  ```
  *   Fix `count(:all)` with eager loading and having an order other than
      the driving table.
      ([Commit](https://github.com/rails/rails/commit/ebc09ed9ad9a04338138739226a1a92c7a2707ee))
  ```
  since it was backported to
  `5-1-stable` by 6df9b69b.

- Remove
  ```
  *   PostgreSQL: Allow pg-1.0 gem to be used with Active Record.
      ([Pull Request](https://github.com/rails/rails/pull/31671))
  ```
  since it was backported to
  `5-1-stable` by a9c06f61.

- Remove
  ```
  *   Fix that after commit callbacks on update does not triggered
      when optimistic locking is enabled.
      ([Commit](https://github.com/rails/rails/commit/7f9bd034c485c2425ae0164ff5d6374834e3aa1d))
  ```
  since it was backported to
  `5-1-stable` by aaee10e6.

- Remove
  ```
  *   Fix regression in numericality validator when comparing Decimal and Float
      input values with more scale than the schema.
      ([Pull Request](https://github.com/rails/rails/pull/28584))
  ```
  since it was backported to
  `5-1-stable` by 5b1c3e5a.
  Note that there was incorrect link to PR,
  original PR is https://github.com/rails/rails/pull/29249.

- Remove
  ```
  *   Fix to working before/after validation callbacks on multiple contexts.
      ([Pull Request](https://github.com/rails/rails/pull/31483))
  ```
  since it was backported to
  `5-1-stable` by 0f7046a7.

- Remove
  ```
  *   Fix implicit coercion calculations with scalars and durations.
      ([Pull Request](https://github.com/rails/rails/pull/29163),
      [Pull Request](https://github.com/rails/rails/pull/29971))
  ```
  since it was backported to
  `5-1-stable` by 51ea27c0,
                  4d82e2aa.

- Remove
  ```
  *   Fix modulo operations involving durations.
      ([Commit](https://github.com/rails/rails/commit/a54e13bd2e8fb4d6aa0aebe59271699a2d62567b))
  ```
  since it was backported to
  `5-1-stable` by 233fa7ea.

- Remove
  ```
  *   Return all mappings for a timezone identifier in `country_zones`.
      ([Commit](https://github.com/rails/rails/commit/cdce6a709e1cbc98fff009effc3b1b3ce4c7e8db))
  ```
  since it was backported to
  `5-1-stable` by 0222ebbe.

- Remove
  ```
  *   Add support for compatibility with redis-rb gem for 4.0 version.
      ([Pull Request](https://github.com/rails/rails/pull/30748))
  ```
  since it was backported to
  `5-1-stable` by 37895311.
  Related to #32252.

Related to #32222, https://github.com/rails/rails/pull/32222#discussion_r174256536.
Follow up a489cc81.

- Add a description of major features in Rails 5.2.
- Add a reference to Pull Request/Commit to every entry in CHANGELOGs,
  note that some of them combined.
- Add section "Ruby on Rails Guides" with notable changes.
- Note that
  - Skipped this since encrypted secrets are already on the way out.
    ```
    *   Add `rails secrets:show` command.
        ([Pull Request](https://github.com/rails/rails/pull/29695))
    ```
  - Skipped this since it was backported all the way to 5-0-stable.
    ```
    *   Make Rails' test runner work better with minitest plugins.
        ([Pull Request](https://github.com/rails/rails/pull/29572))
    ```

Thanks to everyone who has been working on Rails 5.2! <3

Currently, generation of guide is an error in `5_2_release_notes.html`.

```
$ bunele exec rake guides:generate:html
Generating 5_2_release_notes.md as 5_2_release_notes.html
rails/guides/rails_guides/markdown.rb:44:in `dom_id': undefined method `[]' for nil:NilClass (NoMethodError)
	from rails/guides/rails_guides/markdown.rb:106:in `block (2 levels) in generate_structure'
```

It seems that it is an error because there are multiple
`active-storage` anchors.

Since Active Storage is a Major feature, it is unnecessary to show
CHANGELOGs, so remove from `Incompatibilities` section.