Prescribed some review fixes for myself!

Still vulnerable to different file structures. We likely want something
more robust when we tackle in app commands.

Makes sure we get support for `Minitest.after_run` hooks and don't
accidentally run tests twice.

Requires overriding minitest `run` to respect the TESTOPTS variable.

The Rails test runner supports three ways to run tests: directly, via rake, or ruby.

When Running with Ruby ala `ruby -Itest test/models/post_test.rb` our test file would
be evaluated first, requiring `test_helper` and then `active_support/testing/autorun`
that would then require the test file (which it hadn't been before) thus reevaluating
it. This caused exceptions if using Active Support's declarative syntax.

Fix this by shifting around when we set the how we're run to closer mimick the require
order.

If we're running with `bin/rails test` the test command file is run first and we then
set `run_with_rails_extension`, later we hit `active_support/testing/autorun` and do
nothing — because we've been run elsewhere.

If we at this point haven't set `run_with_rails_extension` we've been running with
`ruby` this whole time and thus we set that.

We should always trigger `Minitest.autorun` as it doesn't hurt to call it twice.

Consolidate the two methods into a single one that better brings out the intent of
why they're there.

Revise the require in the test command to use `active_support/testing/autorun`
and spare us the minitest spec syntax as detailed in 5da4d514.

Also move the require to the top of the file for consistency with the rest of
Rails' requires across the project.

Fix code formatting in `#save` RDoc [ci skip]

Noticed that the `validate: false` option for `ActiveRecord::Persistence#save` and `#save!` were not formatted as code like the other examples in the documentation.

AS => Active Support [ci skip]

Fix ActiveSupport::TimeWithZone#in

Previously calls to `in` were being sent to the non-DST aware
method `Time#since` via `method_missing`. It is now aliased to
the DST aware `ActiveSupport::TimeWithZone#+` which handles
transitions across DST boundaries, e.g:

    Time.zone = "US/Eastern"

    t = Time.zone.local(2016,11,6,1)
    # => Sun, 06 Nov 2016 01:00:00 EDT -05:00

    t.in(1.hour)
    # => Sun, 06 Nov 2016 01:00:00 EST -05:00

support minitest after_run

Only search fixture_path for files that can't be found directly

When passed an already-valid file name, prepending the path is likely to
create problems.

This is particularly relevant for #26384, which adds fixture_path
handling to test classes that previously didn't have it: any existing
caller must have been manually locating the file, and we don't want to
break them.

Add #25546 and #25817 to changelog [ci skip]

Fix docs for allowed params to `get` in controller tests  [ci skip]

Fixes #26602

Relevant method documentation:

https://github.com/rails/rails/blob/abe3da9f12710ea85be69b17172bef41220037fc/actionpack/lib/action_dispatch/testing/integration.rb#L14-L43

Serialize JSON attribute value nil as SQL NULL, not JSON 'null'

Test: JSON attribute value nil can be used in where(attr: nil)

Add changelog entry

Prevent circular require of proxy_wrappers.rb, Fixes #26430

Return true if attribute is not changed for update_attribute

- If the attribute is not changed, then update_attribute does not run
  SQL query, this effectively means that no change was made to the
  attribute.
- This change was made in https://github.com/rails/rails/commit/0fcd4cf5
  to avoid a SQL call.
- But the change resulted into `nil` being returned when there was no
  change in the attribute value.
- This commit corrects the behavior to return true if there is no change
  in attribute value. This is same as previous behavior of Rails 4.2
  plus benefit of no additional SQL call.
- Fixes #26593.

fix formatting of `define_callbacks` doc [ci skip]

Single backticks don't work with rdoc.

Fix memoization bug on ActionDispatch::TestRequest#request_method=

TestRequest have been overrriding request_method setter since 2009,
but the actual implementation in Request (not TestRequest) has been
changed since that. Now it's also using @request_method instance
variable to keep the state.

The override in TestRequest have not been calling `super`, which caused
a bug that after accessing #requst_method the value was memoized and
then we've never been able to change it anymore:

```
req = ActionDispatch::TestRequest.create
puts "was: #{req.request_method}" # memoized here
req.request_method = "POST"
puts "became: #{req.request_method}"
```

output:

```
was: GET
became: GET
```

Since the whole purpose of overriding the setter in TestRequest is to
upcase it, I'm changing it to `super(method.to_s.upcase)`

add check of argument

[ci skip] Replace to closing tag

Restore missing Gemfile.lock entries

These lines were lost in https://github.com/rails/rails/commit/12d5c210#diff-e79a60dc6b85309ae70a6ea8261eaf95L191.

fix link to `resque` [ci skip]

`1-x-stable` branch does not exist, `master` is 1.x branch.
Ref: http://words.steveklabnik.com/rescuing-resque-again