README.rdoc was generated to support the doc:app task. Now that
this task is gone we can switch to Markdown, which is nowadays
a better default.

This patch removes the tasks doc:app, doc:rails, and doc:guides.

In our experience applications do not generate APIs using doc:app.
Methods may be certainly documented for maintainers, annotated
with YARD tags, etc. but that is intended to be read with the
source code, not in a separate website. Then, teams also have
typically selected topics written down in Markdown files, or in
a GitHub wiki... that kind of thing.

If a team absolutely needs to generate application documentation
for internal purposes, they can still easily write their own task.

Regarding doc:rails and doc:guides, we live in 2015. We are used
to go to online docs all the time. If you really want access to the
API offline RubyGems generates it for every Rails component unless
you tell it not to, and you can checkout the Rails source code to
read the guides as Markdown, or download them for a Kindle reader.

All in all, maintaining this code does not seem to be worthwhile
anymore.

As a consequence of this, guides (+3 MB uncompressed) won't be
distributed with the rails gem anymore. Of course, guides and API
are going to be still part of releases, since documentation is
maintained alongside code and tests.

Also, time permitting, this will allow us to experiment with novel
ways to generate documentation in the Rails docs server, since
right now we were constrained by being able to generate them in
the user's environment.

nil or false should not be valid argument to the merge method.

Closes #12264

Relation#merge checks if the argument is an array and the only possible
returns of build_default_scope is nil or a Relation.

Doing this we can raise an ArgumentError when Relation#merge receive a
nil value.

Add an `:only` option to `perform_enqueued_jobs` to filter jobs based on type.

type.

This allows specific jobs to be tested, while preventing others from
being performed unnecessarily.

Example:

    def test_hello_job
      assert_performed_jobs 1, only: HelloJob do
        HelloJob.perform_later('jeremy')
        LoggingJob.perform_later
      end
    end

An array may also be specified, to support testing multiple jobs.

Example:

    def test_hello_and_logging_jobs
      assert_nothing_raised do
        assert_performed_jobs 2, only: [HelloJob, LoggingJob] do
          HelloJob.perform_later('jeremy')
          LoggingJob.perform_later('stewie')
          RescueJob.perform_later('david')
        end
      end
    end

Fixes #18802.

Trim space and document :only option.

The `&block` form is more than twice as fast as the manual form of
delegation (and is the code I'd rather write anyway). Unfortunately,
it's still twice as slow on MRI. However, this is enough of a hotspot to
justify giving JRuby special treatment.

I can't currently provide benchmarks in the context of Active Record,
since the JDBC adapters still aren't updated for 4.2, but the actual
work performed (assuming it's been read at least once already) will have
nearly the same performance characteristics as
https://gist.github.com/sgrif/b86832786551aaee74de.

We already validate the keys, so it is better to use the built-in
feature to do this

The same is not true of `define_attribute`, which is meant to be the low
level no-magic API that sits underneath. The differences between the two
APIs are:

- `attribute`
  - Lazy (the attribute will be defined after the schema has loaded)
  - Allows either a type object or a symbol
- `define_attribute`
  - Runs immediately (might get trampled by schema loading)
  - Requires a type object

This was the last blocker in terms of public interface requirements
originally discussed for this feature back in May. All the
implementation blockers have been cleared, so this feature is probably
ready for release (pending one more look-over by me).

Merge #12067 rebasing and improving the code.

Enable number_to_percentage to keep the number's precision by allowing :precision option value to be nil

Conflicts:
	activesupport/CHANGELOG.md
	activesupport/lib/active_support/number_helper.rb
	activesupport/test/number_helper_test.rb

Indicate link_to creates an anchor element

The `link_to` helper generates an HTML anchor element (consisting of opening and closing anchor tags and an element body). The docs currently state the a link tag is generated (which would indicate a tag like `<link>`, which is another valid HTML tag), so this change clarifies that an anchor element is actually generated.

[ci skip]

This reverts commit 9c47b874.

These are (potentially, depending on input) called in several places in
both the router, and Active Record. The code also becomes much cleaner.
This results in ~33% performance gain in both methods.

    Calculating -------------------------------------
                  before    15.696k i/100ms
                  after     19.865k i/100ms
    -------------------------------------------------
                  before    303.064k (± 2.6%) i/s -      1.523M
                  after     446.734k (± 2.4%) i/s -      2.245M

On Ruby 2.2, a warning will be emitted about states not being copied,
because we're calling `super` from a subclass. We can safely ignore it,
however, since we're converting the result back into a HWIDA

Amended json_escape comments

Better docs for AM::Lint::Tests

The existing example seems somewhat forced: is it realistic
to have a model that accepts state in its initializer but
considers it has not been changed? By allowing state changes
to happen only via accessors it seems more natural that new
instances are considered to be unchanged (as they are in AR).

[ci skip]

Use SCHEMA instead of DB_STRUCTURE for specifiying structure file.

Conflicts:
	activerecord/CHANGELOG.md

Fix `test_types_line_up` when column type missing

Extracted silence_stream method to new module in activesupport/testing

Migrating xhr methods to keyword arguments syntax

Also remove the default value since it will be always passed and
Array(nil) returns an empty array

Rename AS::Callback#merge

This will make rake test_sqlite3_mem work again

They are implementation details

Deprecated finders are not supported anymore

Closes #18646

call is too generic

Thse methods are used only inside this class