`test_native_decimal_insert_manual_vs_automatic` exists inside
`unless current_adapter?(:SQLite3Adapter)`. This condition is
duplicated.

Fix doc format for `RecordFetchWarning` [ci skip]

Initial Rails Commands Infrastructure

This is not as good a solution as actually hashing both values, but Ruby
doesn't expose that capability other than allocating the array. Unless we were
to do something silly like have a thread local array that is re-used, I don't
see any other way to do this without allocation. This solution may not be
perfect, but it should reasonably avoid collisions to the extent that we need.

[ci skip] Update PG adapter documentation

Per discussion in pull request #26622:

"Let's change it to PG::Error. The more specific classes mentioned are
subclasses, and the fact the raised exception is a PG::UndefinedColumn
doesn't change the fact that it's also a PG::Error." - matthewd

[ci skip] Clarify Postgresql Documentation

This clarifies the object that +ActiveRecord::Base.connection.execute+
will return when using Postgresql.

Wash out your old! These adhoc scripts are replaced by the new
commands.

Prescribed some review fixes for myself!

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

remove unnecessary `RAILS_ENV` setting

Add info about a502703c to Rails 5 release notes

[ci skip]

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'