Fixes #28988

* Remove trailing spaces.
* Add backticks around method and command.
* Fix indentation.

The css selectors on the generated error pages are too broad (for example `text-align: center` on `body` and thus bleed out to the following pages (say, by pressing the back button) when using Turbolinks. This commit namespaces all the selectors.

The `master` changelog refer back to the `5-1-stable` changelog as a
base. No need to duplicate backported entries in the changelogs on
`master`.

This is a follow up to a6d065e3. When using `form_with` you must supply
field ids manually. Since the scaffold generator is using labels we
need to make sure that they are linked up properly.

The "-j" option was added 5 years ago (https://github.com/rails/rails/commit/d9c39c3a)
when we wanted to support prototype-rails and jquery-rails.
Prototype is not as popular and jQuery is not a requirement anymore.
Still the "-j" option can be used to install *any* gem that ends in "-rails".

This "might" open security issues and does not bring great benefits anymore.

If you know which "-rails"-ending gem you want to install, you can manually
add it to the Gemfile just like any other gem.

The entry for PR #25430 is currently present both in the CHANGELOG
for Rails 5.0 and for Rails 5.1:

https://github.com/rails/rails/blame/9d3a352777c2594123583b0bc02d0dd80f1e385b/railties/CHANGELOG.md#L61-L72

Since the PR was backported to 5-0-stable in #25499, I believe it
should be removed from the CHANGELOG of 5.1, otherwise it looks like
something changed from 5.0 to 5.1

Occasionally we update the file generated by engine.
Therefore, I think that there is a task for updating as well as
application in the engine, it is convenient for updating.

Was added in #25248 by @bluesh55

[ci skip]

These tests may be expansive so let's only allow users to run them
through `bin/rails test:system` or by passing a path to the `test`
command.

The same applies for `bin/rake test`.

Refs #28109.

Includes a script to ease an app's upgrade.

Just dispatch to the command help itself for more info.

Replaces the rake_patterns instance variable with simple require, as
`autorun` will run tests from all eagerly required test files.

Fixes #27801

* If `--skip-git` is not specified initalize git repo
 when creating new rails app

Currently, all rails commands can be executed in engine,
but `server`, `console`, `dbconsole` and `runner` do not work.

This make all rails commands work in engine.
Related to #22588

- Fixes #27591.

[ci skip]

[ci skip]

[ci skip]

Move node_modules, package.json, and yarn.lock file to vendor