Remove stale comment about `ActiveRecord::SchemaDumper.ignore_tables` [skip ci]

Follow up of #31390.

Prevent race condition when resetting time stubs

If the current thread is preempted after the stub has been removed but
before the original method has been restored, then the other thread will
get a `NoMethodError` when it tries to call the method.

Using `silence_redefinition_of_method` instead of `undef_method` ensures
that either the stub or the original method is always in place.

Fix secrets command deprecation message

[ci skip] Update routing guide for Direct & resolved routes

* Added the direct method to routing guide.

This reverts commit a80f81af.

`create_fixtures` doesn't work since at least a94220b6

- The namespacing should be `ActiveRecord::FixtureSet`
- I might be missing something but I'm not sure why `create_fixtures` is useful for nowaday (unless for testing rails internal /shrug) and since it's been that long it wasn't working I think it should be fine to just fire it

Return `nil` instead of `false` if raise `Azure::Core::Http::HTTPError`

[ci skip] Update instrumentation guide for ActiveStorage

* Added `service_delete_prefixed.active_storage`.

Execute a single mogrify command with multiple options rather than one command per option. Permit the use of all mogrify options, not just the ones that fall through to MiniMagick::Image#method_missing.

* If it raise error `Azure::Core::Http::HTTPError`, return `nil` instead of `false` in
  `ActiveStorage::Service::AzureStorageService#delete`.

* Other services behave as same as this.

StreamingTemplateRenderer fails to forward I18n.locale in layouts

`webpack` is assigned but never used in webpack.config.js

Remove whitespace

* Removed webpack const, so it is assigned but never used in webpack.config.js.

Currently, `test_copy_table_with_composite_primary_keys` test fails
depending on execution order. The reproduction step is as follows.

```
$ ARCONN=sqlite3_mem bin/test -w -n "/^(?:CalculationsTest#(?:test_#skip_query_cache\\!_for_a_simple_calculation)|PrimaryKeyAnyTypeTest#(?:test_any_type_primary_key)|ActiveRecord::ConnectionAdapters::SQLite3AdapterTest#(?:test_copy_table_with_composite_primary_keys))$/" --seed 41545
```

The column info is cached by `PrimaryKeyAnyTypeTest#test_any_type_primary_key`,
and the test seems to have failed due to the influence.
So clear cache after testing so as not to affect other tests.

Related: https://travis-ci.org/rails/rails/jobs/313730163#L1788

Change the system tests to set Puma as default server only when the user haven't specified manually another server.

Change the system tests to set Puma as default server only when the user haven't specified manually another server.

CI against JRuby 9.1.15.0

docs: add example for a nil name in link_to

Fix Rails environment when running tests with Ruby

Option parsing happens too late to have any impact on the Rails
environment.  Rails accesses the environment name and memoizes it too
early in the boot process for a commandline option to have any impact on
the database connection, so we'll change this test to set the
environment from an environment variable (and ensure it still works when
running tests with `ruby`)

This reverts commit 9a80f525.

JRuby 9.1.15.0 has been released:
http://jruby.org/2017/12/07/jruby-9-1-15-0.html

When tests are run with just `ruby`, the RAILS_ENV is set to
`development` too early, and we connect to the development database
rather than the test database.

`connection.primary_key` also return composite primary keys, so
`from_primary_key_column` may not be found even if `from_primary_key` is
presented.

```
% ARCONN=sqlite3 be ruby -w -Itest
test/cases/adapters/sqlite3/sqlite3_adapter_test.rb -n
test_copy_table_with_composite_primary_keys
Using sqlite3
Run options: -n test_copy_table_with_composite_primary_keys --seed 19041

# Running:

E

Error:
ActiveRecord::ConnectionAdapters::SQLite3AdapterTest#test_copy_table_with_composite_primary_keys:
NoMethodError: undefined method `type' for nil:NilClass
    /path/to/rails/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb:411:in
    `block in copy_table'
```

This change fixes `copy_table` to do not lose composite primary keys.

Fix issue #30658 by checking explicitly for 'null' referrer

Add headless firefox driver to System Tests