It was removed by mistake at 877a411d

`rack-cors` gem is defined in Gemfile by default only if the api,
not defined by default in rails app.

The Action Cable generators creates four files which need to be removed
if `skip_action_cable` is set.

1. `app/assets/javascripts/cable.coffee`
2. `app/channels/application_cable/channel.rb`
3. `app/channels/application_cable/connection.rb`
4. `config/redis/cable.yml`

Fixes #22669.

It's pretty common for folks to monkey patch `ActiveRecord::Base` to
work around an issue or introduce extra functionality. Instead of
shoving even more stuff in `ActiveRecord::Base`, `ApplicationRecord` can
hold all those custom work the apps may need.

Now, we don't wanna encourage all of the application models to inherit
from `ActiveRecord::Base`, but we can encourage all the models that do,
to inherit from `ApplicationRecord`.

Newly generated applications have `app/models/application_record.rb`
present by default. The model generators are smart enough to recognize
that newly generated models have to inherit from `ApplicationRecord`,
but only if it's present.

Web Console 3.0.0 is compatible with Rails 5, while the 2.x.x releases
aren't.

We are using the same version constraint in the database adapters so
when a new version of the adapter that doesn't work with the version of
rails is released we don't break new applications.

fixes #20042

A lot of scripts assumes the existence of this folder and most would fail if it
is absent.

One example of this is `rake restart` (before the previous commit) – it tries to
`touch tmp/restart.txt`, which would fail if `tmp` does not exist, which was the
case for a freshly-cloned project as `tmp` is `.gitignored` by default.

See #20299.

[Yoong Kang Lim, Sunny Juneja]

Spring seems like an obvious foot gun for the `--dev` setup, presumably you are
about to make lots of changes to the codebase, so it should always reload the
framework.

* Jobs generated now inherent from ApplicationJob
* ApplicationJob inherents from ActiveJob::Base
* Added entry to changelog
Signed-off-by: NJeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Deprecate `required` option in favor of `optional` for belongs_to.

README.rdoc was generated to support the doc:app task. Now that
this task is gone we can switch to Markdown, which is nowadays
a better default.

This patch removes the tasks doc:app, doc:rails, and doc:guides.

In our experience applications do not generate APIs using doc:app.
Methods may be certainly documented for maintainers, annotated
with YARD tags, etc. but that is intended to be read with the
source code, not in a separate website. Then, teams also have
typically selected topics written down in Markdown files, or in
a GitHub wiki... that kind of thing.

If a team absolutely needs to generate application documentation
for internal purposes, they can still easily write their own task.

Regarding doc:rails and doc:guides, we live in 2015. We are used
to go to online docs all the time. If you really want access to the
API offline RubyGems generates it for every Rails component unless
you tell it not to, and you can checkout the Rails source code to
read the guides as Markdown, or download them for a Kindle reader.

All in all, maintaining this code does not seem to be worthwhile
anymore.

As a consequence of this, guides (+3 MB uncompressed) won't be
distributed with the rails gem anymore. Of course, guides and API
are going to be still part of releases, since documentation is
maintained alongside code and tests.

Also, time permitting, this will allow us to experiment with novel
ways to generate documentation in the Rails docs server, since
right now we were constrained by being able to generate them in
the user's environment.

It's a thin layer to provide easy access to sample files throughout
test-cases. This adds the directory `test/fixtures/files` to newly
generated applications.

Rails no longer generates Test::Unit files by default.

Fixes #18473

bebugger doesn't work with Ruby 2.2 so we don't need to support it
anymore

This stems from [a comment](rails#17227 (comment)) by @dhh.
In summary:

* New Rails 5.0 apps will not accept `return false` as a way to halt callback chains, and will not display a deprecation warning.
* Existing apps ported to Rails 5.0 will still accept `return false` as a way to halt callback chains, albeit with a deprecation warning.

For this purpose, this commit introduces a Rails configuration option:

```ruby
config.active_support.halt_callback_chains_on_return_false
```

For new Rails 5.0 apps, this option will be set to `false` by a new initializer
`config/initializers/callback_terminator.rb`:

```ruby
Rails.application.config.active_support.halt_callback_chains_on_return_false = false
```

For existing apps ported to Rails 5.0, the initializers above will not exist.
Even running `rake rails:update` will not create this initializer.

Since the default value of `halt_callback_chains_on_return_false` is set to
`true`, these apps will still accept `return true` as a way to halt callback
chains, displaying a deprecation warning.

Developers will be able to switch to the new behavior (and stop the warning)
by manually adding the line above to their `config/application.rb`.

A gist with the suggested release notes to add to Rails 5.0 after this
commit is available at https://gist.github.com/claudiob/614c59409fb7d11f2931

The changes in #18149 added tests for the app generator, but only fixed
it for the plugin generator (I should have let CI finish though I think
it would have failed as an allowed failure).

https://travis-ci.org/rails/rails/jobs/39190983#L460

 1) Failure:
 AppGeneratorTest#test_psych_gem
 [test/generators/app_generator_test.rb:495]:
 Expected /gem 'psych',\s+'~> 2.0', \s+platforms: :rbx/ to match <snip>
 http://git.io/uuLVag)\ngem 'psych', '~> 2.0', platforms: :rbx\n\n

For the most part of cases --skip-gems option just remove one line in
the Gemfile. This is not worth for the complexity it adds.

Closes #17196

Change position of require active_job

Broken by fbe38c9e

The template runs before the generation of binstubs – this does not
allow to write one, that makes an initial commit to version control.
It is solvable by adding an after_bundle callback.

Since the rubysl-yaml gem doesn't ship with Psych by default because of
its dependency on libyaml, on Rubinius, the default engine is Syck.

However, if we want to be able to run the application safely on
different rubies, we need to make people using Rubinius rely on Psych.

See http://git.io/uuLVag for further information.

We are planning to remove mocha from our test suite because of
performance problems. To make this possible we should stop require mocha
on ActionSupport::TestCase.

This should not affect applications since users still need to add mocha
to Gemfile and this already load mocha.

Added FIXME notes to place that still need mocha removal