* Loop rather than recurse in retrieve_connection_pool
* Key the hash by class rather than class name. This avoids creating
  unnecessary strings.

This reverts commit 7256cb53, reversing
changes made to 6ebe22c3.

Reason: A test was failing.

This reverts commit e4b33b08.

https://github.com/rails/rails/pull/7452#issuecomment-8094302

the example for contraint( :ip => XXXX) has an invalid regex

Since it uses request and response methods

Fix build about TemplateDigestorTest.

Fixes warning: & interpreted as argument prefix

Better ActionView::Digestor nested template inference

A missing require is added to fix build. When performing rake test:isolated in actionmailer, test/base_test.rb was break.

Fix grammar

Fix markdown rendering of the ActionPack changelog [ci skip]

escape the '.'s  

Added controller-level etag additions that will be part of the action etag computation *Jeremy Kemper/DHH*

Add automatic template digests to all CacheHelper#cache calls (originally spiked in the cache_digests plugin) *DHH*

Add Missing Keys from Journey on Failed URL Format

We need to anchor to remove the extension. In addition to
be the correct way to do that, files in ~/.rbenv get that
.rb removed, so it is a real source of bugs, as reported in

https://github.com/rails/rails/commit/b33700f5580b4cd85379a1dc60fa341ac4d8deb2#commitcomment-1781840

Fixed indendation

Changes in old branches needed to be manually synched in CHANGELOGs of newer ones.
This has proven to be brittle, sometimes one just forgets this manual step.
With this commit we switch to CHANGELOGs per branch. When a new major version is
cut from master, the CHANGELOGs in master start being blank.

A link to the CHANGELOG of the previous branch allows anyone interested to
follow the history.

Nowadays circular autoloads do not work, but the user gets a NameError
that says some constant is undefined. That's puzzling, because he is
normally trying to autoload a constant he knows can be autoloaded.
With this check we can give a better error message.

Fix method redefined warnings.

Fixes warnings when executing rake test in ActionMailer. 

Fixes warnings when executing rake test in ActionMailer. Related to 582a7f45

Tiny fixes in railties/test/application.