added more accurate test for add_on_empty

with the current tests, if delete the assignment of is_empty in add_on_empty method
the tests not fail. With this test, if we delete is_empty, the test fails

delete duplicated tests in AR base_test.rb

Raising an error when query methods have blank arguments.

These are duplicated with the tests which are in relations_test.rb

Closes #9302

Require ActiveSupport dependencies in ActionDispatch::Http::URL

Allows us to use url_for and friends in isolation.

Most application developers shouldn't be adding paths to
`config.autoload_paths` as it won't be eagerly loaded so
remove it from the generated config/application.rb file.

If a developer does want to autoload from paths outside of the app
directory then they should add the path to `config.eager_load_paths`
as these paths are also autoloaded as well.

Whilst autoloading is known to be not threadsafe, leaving it in place
is a softer solution than failing hard when an application is deployed.

Many older applications will have paths added to `autoload_paths` and
ideally these should be eagerly loaded to be threadsafe. However one
of these paths is quite often lib which could lead to unintended
consequences due to the 'junk drawer' nature of this directory.

Developers should refrain from adding paths to `autoload_paths` or
`eager_load_paths` and use custom folders inside app for code that
needs to be eagerly loaded and use `require` or `require_dependency`
to explicitly load code from other locations.

Because of the possibility of lib being unintentionally eager loaded
it's been agreed that we'll leave autoload paths and eager load paths
separate for Rails 4.0.

This reverts commit 0757b338.

Conflicts:
	railties/CHANGELOG.md

Somehow I missed this method, which was then throwing an error
when viewing routes as HTML.

Make @rubys happy: ✔

Thanks @sikachu. 😅

Thanks @sikachu. ❤

Print message on stderr when no routes are defined.

Print a message in both `rake routes` and at GET "/rails/info/routes"
that lets you know you have no routes defined, as well as linking to the
Rails Guide on the topic.

Add headings to rake routes table

Document changes from #7968 in Upgrading Guide

see: https://github.com/blog/1406-namespaced-gists

Return false in toggle function on error pages

Add test for ActiveRecord::Base#create

[ci skip]

Removed an old require of an MD5 digest which is no longer used.

This revision makes the terminology uniform with the rest of the file.
In general we describe these methods in terms of the adapter, rather
than the database. (As a side note, if we wanted to refer to the
database we would write "PostgreSQL".)

It was supposed to be removed by the preceding two reversions but I did
them in the wrong order.