Plus a couple of related ActionPack patches.

".. with __dir__ we can restore order in the Universe." - by @fxn

Related to 5b8738c2

sub_template_message distracts Rails.root from its message only when Rails.root is defined,
and Rails.root is defined at tools/test.rb

When rendering heterogeneous collection using `render @collection` or
`render partial: @collection`, the expected `<partial_name>_iteration`
variable is missing due to `find_template` not having the name of the
iteration variable included in its cache keys.

(I personally prefer writing one string in one line no matter how long it is, though)

assert [1, 3].includes?(2) fails with unhelpful "Asserting failed" message

assert_includes [1, 3], 2 fails with "Expected [1, 3] to include 2" which makes it easier to debug and more obvious what went wrong

Style/SpaceBeforeBlockBraces
Style/SpaceInsideBlockBraces
Style/SpaceInsideHashLiteralBraces

Fix all violations in the repository.

The current code base is not uniform. After some discussion,
we have chosen to go with double quotes by default.

An optimization was introduced in
https://github.com/rails/rails/commit/27f4ffd11a91b534fde9b484cb7c4e515ec0fe77
which tried to `#to_ary` the collection to prevent unnecessary queries
for ActiveRecord scopes/relations. If the given collection did not
respond to `#to_ary`, and empty collection was returned. That meant you
couldn't use collections built from `Enumerator` nor `Enumerable`.

With this change, `#collection_from_options` will attempt the
optimization, but fall back to passing along the given collection,
as-is.

In PR #24929 the changelog was updated to make note that while the new
template handler was changed to raw this changed the behavior when
outputting plain html or js files. Previously ERB would output the files
unescaped. Changing the default handler to RAW meant that these same
files would be rendered as escaped rather than as js or html.

Because of this change in behavior and after the discussion #24949 in we
decided to change the behavior of the Raw handler to output html_safe
strings by default.

Now files rendered with the default handler (raw) render the file
unescaped.

When rendering a collection with a partial whose filename contains a dot, e.g.
"customer.mobile", we would set a `locals[:'customer.mobile']` variable instead
of, as in earlier versions of Rails, `locals[:customer]`.

This bug was introduced in da9038ea.

Having collection caching that wraps templates and automatically tries
to infer if they are cachable proved to be too much of a hassle.

We'd rather have it be something you explicitly turn on.

This removes much of the code and docs to explain the previous automatic
behavior.

This change also removes scoped cache keys and passing cache_options.

- Changed formatted_code_for to return array of logs to be tagged for each line
- Changed some render tests to match new behaviour of return

Fixes #22979

CVE-2016-0752

This fixes the case when you try to render an html you know safe and the
file is named something.html. With this commit the content of the html
won't be escaped anymore because AV won't use Raw handler and choose
Html handler instead.

Introduced in e56c6354, `CacheHelper#fragment_cache_key` is a duplicate of `ActionController::Caching::Fragments#fragment_cache_key`.

We now require the view to provide this method on its own (as with `view_cache_dependencies`); `ActionController::Caching::Fragments` exports its version as a `helper_method`.

This commit fixes the bug convering `false` to `locals[as]` when
`options[:object]` is `false` (close #22260).

Adds the `virtual_path` option to `cache_fragment_name` so it can
be provided when needed.

That allows `cache_collection_render` to get the appropriate cache
key with the digest generated based on the template and prevent
collision with other templates that cache the same collection.

When one rendered a partial template without specifying an object
or a collection (e.g. <%= render partial: 'partial_name' %>), Rails
would make an object called :partial_name available in local_assigns.
I don't think this was the intended behavior, since no local variable
called 'partial_name' gets defined in the view.

Collections can take advantage of `multi_read` if they render one template
and their partials begin with a cache call.

The cache call must correspond to either what the collections elements are
rendered as, or match the inferred name of the partial.

So with a notifications/_notification.html.erb template like:

```ruby
<% cache notification %>
  <%# ... %>
<% end %>
```

A collection would be able to use `multi_read` if rendered like:

```ruby
<%= render @notifications %>
<%= render partial: 'notifications/notification', collection: @notifications, as: :notification %>
```

The testing of error messages have been implemented wrongly a few times.
This is an attempt to fix it.

For example, some of these test should have failed with the new code.
The reason they are not failling with the new string is the fact they
were not being tested beforehand.

Makes caching a collection of template partials faster using `read_multi`
on the Rails cache store.

Some caching implementations have optimized `read_multi` so we don't have
to check in the cache store for every template.

because the partial renderer would not create an lvar per each template since c67005f2

before this PR IDENTIFIER_ERROR_MESSAGE could lead to misunderstand the convention of partial name.
Added OPTION_AS_ERROR_MESSAGE for unvalid charter in as option.