In order to keep this method compatible with the Ruby 2.5 version of Hash#slice.
This bahavior is actually slightly incompatibile with previous versions of Active Support
but it might not cause a real problem, since HWIA, the biggest use case of Hash subclassing here,
already overrides `slice` to return another HWIA.

* Add missing credit
* Add backticks
* Fix indentation
* Remove trailing spaces

And some minor tweaks.

See the changelog entry.

Remove `secrets.secret_token` from the bug report templates,
since we don't accept bug reports for Rails versions that
don't support a `secret_key_base`.

[ claudiob & Kasper Timm Hansen ]

Currently, `#transform_values`, `#select` and `#reject` return instance
of `HashWithIndifferentAccess`. But `#transform_keys` returns instance
of Hash. This behavior is a bit confusing.

I think that `HashWithIndifferentAccess#transform_keys` should also return
instance of `HashWithIndifferentAccess` as well as other methods.

Both classes now have a rotate method where new instances are added for
each call. When decryption or verification fails the next rotation
instance is tried.

* WIP: Add credentials using a generic EncryptedConfiguration class

This is sketch code so far.

* Flesh out EncryptedConfiguration and test it

* Better name

* Add command and generator for credentials

* Use the Pathnames

* Extract EncryptedFile from EncryptedConfiguration and add serializers

* Test EncryptedFile

* Extract serializer validation

* Stress the point about losing comments

* Allow encrypted configuration to be read without parsing for display

* Use credentials by default and base them on the master key

* Derive secret_key_base in test/dev, source it from credentials in other envs

And document the usage.

* Document the new credentials setup

* Stop generating the secrets.yml file now that we have credentials

* Document what we should have instead

Still need to make it happen, tho.

* [ci skip] Keep wording to `key base`; prefer defaults.

Usually we say we change defaults, not "spec" out a release.

Can't use backticks in our sdoc generated documentation either.

* Abstract away OpenSSL; prefer MessageEncryptor.

* Spare needless new when raising.

* Encrypted file test shouldn't depend on subclass.

* [ci skip] Some woordings.

* Ditch serializer future coding.

* I said flip it. Flip it good.

* [ci skip] Move require_master_key to the real production.rb.

* Add require_master_key to abort the boot process.

In case the master key is required in a certain environment
we should inspect that the key is there and abort if it isn't.

* Print missing key message and exit immediately.

Spares us a lengthy backtrace and prevents further execution.

I've verified the behavior in a test app, but couldn't figure the
test out as loading the app just exits immediately with:

```
/Users/kasperhansen/Documents/code/rails/activesupport/lib/active_support/testing/isolation.rb:23:in `load': marshal data too short (ArgumentError)
	from /Users/kasperhansen/Documents/code/rails/activesupport/lib/active_support/testing/isolation.rb:23:in `run'
	from /Users/kasperhansen/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/minitest-5.10.2/lib/minitest.rb:830:in `run_one_method'
	from /Users/kasperhansen/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/minitest-5.10.2/lib/minitest/parallel.rb:32:in `block (2 levels) in start'
```

It's likely we need to capture and prevent the exit somehow.
Kernel.stub(:exit) didn't work. Leaving it for tomorrow.

* Fix require_master_key config test.

Loading the app would trigger the `exit 1` per require_master_key's
semantics, which then aborted the test.

Fork and wait for the child process to finish, then inspect the
exit status.

Also check we aborted because of a missing master key, so something
else didn't just abort the boot.

Much <3 to @tenderlove for the tip.

* Support reading/writing configs via methods.

* Skip needless deep symbolizing.

* Remove save; test config reader elsewhere.

* Move secret_key_base check to when we're reading it.

Otherwise we'll abort too soon since we don't assign the secret_key_base
to secrets anymore.

* Add missing string literal comments; require unneeded yaml require.

* ya ya ya, rubocop.

* Add master_key/credentials after bundle.

Then we can reuse the existing message on `rails new bc4`.

It'll look like:

```
Using web-console 3.5.1 from https://github.com/rails/web-console.git (at master@ce985eb)
Using rails 5.2.0.alpha from source at `/Users/kasperhansen/Documents/code/rails`
Using sass-rails 5.0.6
Bundle complete! 16 Gemfile dependencies, 72 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.
Adding config/master.key to store the master encryption key: 97070158c44b4675b876373a6bc9d5a0

Save this in a password manager your team can access.

If you lose the key, no one, including you, can access anything encrypted with it.

      create  config/master.key
```

And that'll be executed even if `--skip-bundle` was passed.

* Ensure test app has secret_key_base.

* Assign secret_key_base to app or omit.

* Merge noise

* Split options for dynamic delegation into its own method and use deep symbols to make it work

* Update error to point to credentials instead

* Appease Rubocop

* Validate secret_key_base when reading it.

Instead of relying on the validation in key_generator move that into
secret_key_base itself.

* Fix generator and secrets test.

Manually add config.read_encrypted_secrets since it's not there by default
anymore.

Move mentions of config/secrets.yml to config/credentials.yml.enc.

* Remove files I have no idea how they got here.

* [ci skip] swap secrets for credentials.

* [ci skip] And now, changelogs are coming.

* Add test for the new exception of delegate_missing_to

* Add a changelog entry

* Only check for nil if NoMethodError was raised

* Make method private

* Have to pass both target name and value

* Inline the re-raise

[Rafael Mendonça França + Anton Khamets]

Light grammar edits.

[ci skip]

[ci skip]

String#camelize was returning nil without any feedback when an
invalid option was passed as parameter. This update makes the method
to raises an ArgumentError when the option passed is invalid, similar
to what Ruby does for String#downcase (and others) in 2.4.1.

https://ruby-doc.org/core-2.4.1/String.html#method-i-downcase

Rails 5.1 introduce an `ActiveSupport::Duration::Scalar` class as
a wrapper around a numeric value as a way of ensuring a duration
was the outcome of an expression. However the implementation was
missing support for modulo operations. This commit adds support
for those operations and should result in a duration being
returned from expressions involving them.

Fixes #29603 and #29743.

PR #29163 introduced a change in behavior when a duration was
the denominator in a calculation - this was incorrect as dividing
by a duration should always return a `Numeric`. The behavior of
previous versions of Rails has been restored.

Fixes #29592.

The paragraphs retread ground covered by the title and the usage examples,
so let's just remove them.

[ Assain Jaleel & Kasper Timm Hansen ]

[ci skip]

[ Assain Jaleel & Kasper Timm Hansen ]

Rails.cache.write_multi foo: 'bar', baz: 'qux'

Plus faster `fetch_multi` with stores that implement `write_multi_entries`.
Keys that aren't found may be written to the cache store in one shot
instead of separate writes.

The default implementation simply calls `write_entry` for each entry.
Stores may override if they're capable of one-shot bulk writes, like
Redis `MSET`.

[ci skip]

[ci skip]

* Allow a default value to be declared for class_attribute

* Convert to using class_attribute default rather than explicit setter

* Removed instance_accessor option by mistake

* False is a valid default value

* Documentation

* Add ActiveSupport::CurrentAttributes to provide a thread-isolated attributes singleton

* Need to require first

* Move stubs into test namespace.

Thus they won't conflict with other Current and Person stubs.

* End of the line for you, whitespace!

* Support super in attribute methods.

Define instance level accessors in an included module such that
`super` in an overriden accessor works, akin to Active Model.

* Spare users the manual require.

Follow the example of concerns, autoload in the top level Active Support file.

* Add bidelegation support

* Rename #expose to #set. Simpler, clearer

* Automatically reset every instance.

Skips the need for users to actively embed something that resets
their CurrentAttributes instances.

* Fix test name; add tangible name value when blank.

* Try to ensure we run after a request as well.

* Delegate all missing methods to the instance

This allows regular `delegate` to serve, so we don't need bidelegate.

* Properly test resetting after execution cycle.

Also remove the stale puts debugging.

* Update documentation to match new autoreset

Previously calculations where the scalar is first would be converted
to a duration of seconds but this causes issues with dates being
converted to times, e.g:

    Time.zone = "Beijing"           # => Asia/Shanghai
    date = Date.civil(2017, 5, 20)  # => Mon, 20 May 2017
    2 * 1.day                       # => 172800 seconds
    date + 2 * 1.day                # => Mon, 22 May 2017 00:00:00 CST +08:00

Now the `ActiveSupport::Duration::Scalar` calculation methods will try
to maintain the part structure of the duration where possible, e.g:

    Time.zone = "Beijing"           # => Asia/Shanghai
    date = Date.civil(2017, 5, 20)  # => Mon, 20 May 2017
    2 * 1.day                       # => 2 days
    date + 2 * 1.day                # => Mon, 22 May 2017

Fixes #29160, #28970.

Previously apply_inflections would only use the :en uncountables
rather then the ones for the locale that was passed to pluralize or
singularize.

This changes apply_inflections to take a locale which it will use to
find the uncountables.

* Fix indentation.
* Add backticks.

* Remove trailing spaces.
* Add backticks around method and command.
* Fix indentation.

Send deprecation horizon and gem name as arguments to deprecation heavier handler, and make sure they are used for the ActiveSupport::Notifications message.

Support `:offset` in `Time#change` and `:zone` or `:offset`
in `ActiveSupport::TimeWithZone#change`.

Fixes #28723.

Was looking through #28402, and realized the CHANGELOG.md entry is in the wrong
place. Sorry we didn't catch this during code review 😢

[ci skip]

`fetch_values` was added to Hash in Ruby 2.3.0:
  https://bugs.ruby-lang.org/issues/10017

This patch adds an implemention for instances of HWAI, in line
with the existing definitions of `fetch` and `values_at`.