As requested by David in 23233.

Be consistent in testing outputs from railties test and use /bin/rails everywhere(the default behaviour now) instead of mix of /bin/rake /bin/rails everywhere
[Ryo Hashimoto & Vipul A M]

- Using `references` or `belongs_to` in migrations will always add index
  for the referenced column by default, without adding `index:true` option
  to generated migration file.
- Users can opt out of this by passing `index: false`.
- Legacy migrations won't be affected by this change. They will continue
  to run as they were before.
- Fixes #18146

- Fixes #23137.

Because the form is not in the Rails API,
`per_form_csrf_tokens` initializer I think unnecessary.

Forgot to remove it, when I changed the expectations in 88881d2b.

If running `bin/rails t test/models/bunny_test.rb:` we'd implicitly run all the
tests in the bunny test. I now highly doubt that people would ever put in a line
filter without a line *and* want that to mean run all tests in that file.

Instead, change regex to require a line digit after the colon, so runs without a
line at the end would fail to require the test file.

This also has the side benefit of breaking requiring a file with many colons:
`bin/rails t test/models/bunny_test.rb:::::::::::::4`

Think this means I've had enough colonoscopy to last me through the year :)

- Modify the default regex to not match hidden files

Fix bug (#22811) that occurs when rails server is started in daemon mode
and optional path to the `server.pid` file is omitted. Store default path
in a constant instead of evaluating it multiple time using `File.expand_path`.

The bug in detail: The server startup procedure crashes, since it tries to
open a file at `/tmp/pids/server.pid` instead of
`<path to project>/tmp/pids/server.pid`. This bug was introduced in 51211a94
when Rack was upgraded from version 1.x to 2.x. Since version 2.x,
Rack does not memoize the options hash [1], and as a consequence
`Rails::Server#default_options` will be evaluated multiple times.
The hash returned by `Rails::Server#default_options` holds the default path
to the `server.pid` file. The path is generated with the method
`File.expand_path`. However, the return value of this method depends on the
current working directory [2], which changes once `Process.daemon` is invoked
by `Rack::Server#daemonize_app` and the process is detached from the current
shell.

Close #22811

[1]https://git.io/vzen2
[2]http://ruby-doc.org/core-2.1.5/File.html#method-c-expand_path

since 9446e38b, generated mailer inherents from ApplicationMailer,
ApplicationMailer is required in the mountable engine.

Closes #23027.

This does not restore complete backwards compatibility. It simply passes
the contets of the `TEST` env to the new runner.

This removes the following warnings.

```
test/application/rake_test.rb:33: warning: ambiguous first argument; put parentheses or a space even after `/' operator
test/application/rake_test.rb:43: warning: ambiguous first argument; put parentheses or a space even after `/' operator
```

- Avoided truncating all files if no ENV['LOGS'] specified
- Updated task to accept LOGS=all for truncating all files from log/ i.e. log/*log
- If no LOGS specified will truncates standard environment log files i.e. 'development,test,production'
- CHANGELOG & guide update added
- bin/setup test cases fixed

This PR introduces a key/value type store to Active Record that can be used for storing internal values. It is an alternative implementation to #21237 cc @sgrif @matthewd.

It is possible to run your tests against your production database by accident right now. While infrequently, but as an anecdotal data point, Heroku receives a non-trivial number of requests for a database restore due to this happening. In these cases the loss can be large.

To prevent against running tests against production we can store the "environment" version that was used when migrating the database in a new internal table. Before executing tests we can see if the database is a listed in `protected_environments` and abort. There is a manual escape valve to force this check from happening with environment variable `DISABLE_DATABASE_ENVIRONMENT_CHECK=1`.

In high volume applications it can be very difficult to figure out what is happening in logs because each request is not easily identified. For example 3 requests could look something like this:

```
Started GET "/" for 72.48.77.213 at 2016-01-06 20:30:21 +0000
  Rendered welcome/index.html.erb within layouts/application (0.1ms)
Started GET "/" for 72.48.77.213 at 2016-01-06 20:30:22 +0000
Started GET "/" for 72.48.77.213 at 2016-01-06 20:30:23 +0000
  Rendered welcome/index.html.erb within layouts/application (0.1ms)
Processing by WelcomeController#index as HTML
Completed 200 OK in 5ms (Views: 3.8ms | ActiveRecord: 0.0ms)
Processing by WelcomeController#index as HTML
  Rendered welcome/index.html.erb within layouts/application (0.1ms)
Completed 200 OK in 5ms (Views: 3.8ms | ActiveRecord: 0.0ms)
  Processing by WelcomeController#index as HTML
Completed 200 OK in 5ms (Views: 3.8ms | ActiveRecord: 0.0ms)
```

The `:request_id` log tag ensures that each request is tagged with a unique identifier. While they are still interleaved it is possible to figure out which lines belong to which requests. Like:

```
[c6034478-4026-4ded-9e3c-088c76d056f1] Started GET "/" for 72.48.77.213 at 2016-01-06 20:30:21 +0000
[c6034478-4026-4ded-9e3c-088c76d056f1]  Rendered welcome/index.html.erb within layouts/application (0.1ms)
[abuqw781-5026-6ded-7e2v-788c7md0L6fQ] Started GET "/" for 72.48.77.213 at 2016-01-06 20:30:22 +0000
[acfab2a7-f1b7-4e15-8bf6-cdaa008d102c] Started GET "/" for 72.48.77.213 at 2016-01-06 20:30:23 +0000
[abuqw781-5026-6ded-7e2v-788c7md0L6fQ]  Rendered welcome/index.html.erb within layouts/application (0.1ms)
[c6034478-4026-4ded-9e3c-088c76d056f1] Processing by WelcomeController#index as HTML
[c6034478-4026-4ded-9e3c-088c76d056f1] Completed 200 OK in 5ms (Views: 3.8ms | ActiveRecord: 0.0ms)
[abuqw781-5026-6ded-7e2v-788c7md0L6fQ] Processing by WelcomeController#index as HTML
[abuqw781-5026-6ded-7e2v-788c7md0L6fQ]  Rendered welcome/index.html.erb within layouts/application (0.1ms)
[abuqw781-5026-6ded-7e2v-788c7md0L6fQ] Completed 200 OK in 5ms (Views: 3.8ms | ActiveRecord: 0.0ms)
[acfab2a7-f1b7-4e15-8bf6-cdaa008d102c]  Processing by WelcomeController#index as HTML
[acfab2a7-f1b7-4e15-8bf6-cdaa008d102c] Completed 200 OK in 5ms (Views: 3.8ms | ActiveRecord: 0.0ms)
```

Now if you have the logs and you find this unique ID you can filter to only look at information from that request. So a filtered log output would be very clear:

```
[c6034478-4026-4ded-9e3c-088c76d056f1] Started GET "/" for 72.48.77.213 at 2016-01-06 20:30:21 +0000
[c6034478-4026-4ded-9e3c-088c76d056f1]  Rendered welcome/index.html.erb within layouts/application (0.1ms)
[c6034478-4026-4ded-9e3c-088c76d056f1] Processing by WelcomeController#index as HTML
[c6034478-4026-4ded-9e3c-088c76d056f1] Completed 200 OK in 5ms (Views: 3.8ms | ActiveRecord: 0.0ms)
```

In addition to this benefit the `:request_id` can be set via the `X-Request-ID` header so that the same request could be traced between multiple components. For example a request comes in Nginx (or another load balancer) could assign a request id. As the load balancer processes the request I can log using that id, then when the request is passed on to Rails, the same id is used. That way if a problem is determined to be not caused in Rails it could be traced back to other components with the same ID. You can set a value in nginx for example using something like this:

```
  location / {
      proxy_pass http://upstream;
      proxy_set_header X-Request-Id $pid-$msec-$remote_addr-$request_length;
  }
# http://stackoverflow.com/questions/17748735/setting-a-trace-id-in-nginx-load-balancer
```

Heroku sets this header value so problems like timeouts that are logged by like router can be traced back to specific request within the application.

Whether you are using components that are setting request ID or not, all production applications can benefit from the additional debugging information of having a unique identifier for all requests. This change will only affect new applications, anyone can opt out by commenting or removing the line in `config/production.rb`.

Since the `#file_name` that not consideration for the namespace, if generate a controller with a namespace,
not the correct url helper generation, it had become an error to run the test.

Modified to generate the correct url helper, even if it is produced a namespace with controller.

Add tests for detecting bad options for runner

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.

generator template.

The errors message only was not displayed, as if it did not use the inline reporting,
modified to also information the method name and the like in error are displayed.

```
# before
Failed assertion, no message given.

bin/rails test test/models/user_test.rb:5
```

```
# after
Failure:
UserTest#test_the_truth:
Failed assertion, no message given.

bin/rails test test/models/user_test.rb:5
```

Our logic is complex now and we don't need to check the version to asset
the behavior so I'm removing the checking here.

We originally chose to apply very strict versioning on the `rails` entry
in the Gemfile, because our future versioning policy was not strongly
defined.

Now it is, and our policy is very much designed on the expectation that
people will regularly update to the latest patch level in their release
series... so we should encourage that.

Of course, Gemfile.lock will do its job and prevent unplanned updates,
just as it does for every other gem in the bundle... but if you run
`bundle update`, we want to get you the latest bug/security fixes
without requiring a manual edit of the Gemfile entry.

Our current version could be a few different shapes, so it takes a bit
of work to find the right specifier, but in principle, we match anything
of the form x.y.*, where x.y matches our current release series.