Clear attribute changes after handling locking

[ci skip] Fix bad examples in rdoc

fix formatting of `Cache::Store#fetch` [ci skip]

Single backticks don't work with rdoc.

Fix small grammar issue introduced in #26382

[ci skip]

improve error message when include assertions fail

assert [1, 3].includes?(2) fails with unhelpful "Asserting failed" message

assert_includes [1, 3], 2 fails with "Expected [1, 3] to include 2" which makes it easier to debug and more obvious what went wrong

Update ActiveModel::Dirty Doc to be simpler to understand

Rename test to match what it does

DRYing duplicate methods

[fixes #26441]

fix typo in `add_column` doc [ci skip]

Commit d270da56 changed the `form_for` API from `:object_name` to `:as`.
It also change the related test body, but not its title, which is changed here.

See https://github.com/rails/rails/commit/d270da569efeabd7cd563028816452236713aa9f#diff-52455f1e82acf12551bc5e7e26b82008

I realize this is a small commit but I was having trouble understanding what
the test was about since there is no "object_name" in the code.
I imagine the same may happen to other developers, therefore this commit.

Update ActiveModel::Dirty Doc [ci skip]

Fix potentially misleading example.

* added bug report template for migrations

remove useless `gemfile` option

Correct `render text:` deprecation message

Improve assert_response helper

The default Content-Type is `text/html`, not `text/plain`.

Without this the changes to the lock version column will stick around
even after `touch` returns.

Before:

    model.touch
    model.changes
    # => {"lock_version"=>[0, "1"]}

After:

    model.touch
    model.changes
    # {}

When the check is failed, print the actual response body if it's not too large.
This could improve productivity when writing new tests.

Before:

```
ThemeEditorIntegrationTest#test_whatever
    Expected response to be a <200: ok>, but was a <422: Unprocessable Entity>.
Expected: 200
  Actual: 422
```

After:

```
ThemeEditorIntegrationTest#test_whatever
    Expected response to be a <200: ok>, but was a <422: Unprocessable Entity>.
Expected: 200
  Actual: 422
Response body: {"errors":["Invalid settings object for section '1'"]}
```

Move comment about disconnecting pool close to comment about preload

fix broken generators test

Fix broken comments indentation caused by rubocop auto-correct [ci skip]

All indentation was normalized by rubocop auto-correct at 80e66cc4.
But comments was still kept absolute position. This commit aligns
comments with method definitions for consistency.

- These two comments are connected to each other so kept them back to back.

Follow up to 92703a9e

Master based applications should be pointing to master

Address warning: ambiguous first argument

* activerecord/mysql2: Avoid setting @connection to nil, just close it

Backport of https://github.com/rails/rails/pull/26434

* Add a CHANGELOG entry

Disconnects all connections in the pool before forking.