Although the spec[1] is defined in such a way that a trailing semi-colon
is valid it also doesn't allow a semi-colon by itself to indicate an
empty policy. Therefore it's easier (and valid) just to omit it rather
than to detect whether the policy is empty or not.

[1]: https://www.w3.org/TR/CSP2/#policy-syntax

Setting up the request environment was accidentally creating a CSP
as a consequence of accessing the option - only set the instance
variable if a block is passed.

This reverts commit 86f7c269, reversing
changes made to 5ece2e4a.

If a policy is set then we should generate it even if it's empty.
However what is happening is that we're accidentally generating an
empty policy when the initializer is commented out by default.

rubocop single space after assignment

Fixes #32021.

The purpose of keeping app/views folder in API apps is that it's used for
mailer views so doesn't makes sense to keep it when Action Mailer is skipped.

* Don't use :: for class methods, we don't do that elsewhere.

* Don't install a needless method on minitest. Prefer assigning the
  reporter anyway as that's what minitest does internally.

* Don't bother opting out when the reporter ain't a Minitest::CompositeReporter.
  It's hardcoded: https://github.com/seattlerb/minitest/blob/005a3ba42c07d04797e2d00ac2c53e3be127c12f/lib/minitest.rb#L125
  And overrides have to create delegate reporters:
  https://github.com/kern/minitest-reporters/blob/1018b1b42f34b01d4de179c8aad2fa06771fe9b0/lib/minitest/minitest_reporter_plugin.rb#L72

Skip generating empty CSP header when no policy is configured

`Rails.application.config.content_security_policy` is configured with no
policies by default. In this case, Content-Security-Policy header should
not be generated instead of generating the header with no directives.
Firefox also warns "Content Security Policy: Couldn't process unknown
directive ''".

3acc5d6e was changed the order of scope evaluation from through scope to
the association's own scope to be prioritized over the through scope.
But the sorting order will be prioritized that is evaluated first. It is
unintentional effect, association scope's sorting order should be
prioritized as well.

Fixes #32008.

Fix active_job_basics.md callbacks example [ci skip]

This reverts commit cf4f05a7.

Since Rails 6 requires Ruby 2.4.1+.

So `2.4` would match `2.4.1` (due to an rvm alias) rather than matching
the latest `2.4.3` release.

This faithfully preserves grapheme clusters (characters composed of other
characters and combining marks) and other multibyte characters.

```ruby
"foo".freeze.strip_heredoc.frozen?  # => true
```

Fixes the case where frozen string literals would inadvertently become
unfrozen:

```ruby

foo = <<-MSG.strip_heredoc
  la la la
MSG

foo.frozen?  # => false !??
```

Prepare bug report templates for Rails 6.0 development

Add missing `require "active_support"` in `guides/bug_report_templates/generic_gem.rb`

Fixes typos

Skipping over 2.4.0 to sidestep the `"symbol_from_string".to_sym.dup` bug.

References #32028

Object#blank? used to be used in this file, but it's not anymore.

This avoids a monkey-patch, for those who want to use just this isolated
feature of ActiveSupport.

* Global ignores at toplevel .gitignore
* Component-specific ignores in each toplevel directory
* Remove `actionview/test/tmp/.keep` for JRuby

```
rm actionview/test/tmp/ -fr
cd actionview/
bundle exec jruby -Itest test/template/digestor_test.rb
```

Related to #11743, #30392.

Closes #29978.

Closes #31998

Some attr_readers should be `protected` instead of `private`

See https://travis-ci.org/rails/rails/builds/342800276

See https://github.com/ruby/ruby/blob/ruby_2_3/NEWS

Multipart file uploads are very rare in API only apps so don't include Rack::TemfileReaper in default middleware stack for API only apps

Fix custome serializer setting

References 89bcca59

Use SuppressedSummaryReporter and Rails::TestUnitReporter only if needed

Fix array routing constraints

Make sure that when transforming the keys of a HashWithIndifferentAccess
we can still access with indifferent access in Ruby 2.5.

Closes #32007.