In Rails engine `Rails.root `returns the path of the dummy application.
Therefore, there is no `tmp` directly where the test is running, so can
not get the screenshot.
For this reason, instead of directly specifying tmp, retrive screenshot by
relative path from the current directory.

Fixes #30405

https://travis-ci.org/rails/rails/jobs/268599781#L784

Use tt in doc for action_pack [ci skip]

Fix `can't modify frozen String` error in `display_image`

Use tt in doc for action_mailer [ci skip]

Use typewriter in doc for Action Cable [ci skip]

Fix broken doc for Active Record [ci skip]

Without this, `display_image` raises an error as follwing:

```
RuntimeError: can't modify frozen String
    rails/actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb:72:in `display_image'
    rails/actionpack/test/dispatch/system_testing/screenshot_helper_test.rb:40:in `block (2 levels) in <class:ScreenshotHelperTest>'
```

Enable links in Active Storage docs [ci skip]

Add :nodoc: for ActiveRecord::AttributeMethods [ci skip]

Fix link in doc for active storage [ci skip]

This regression was caused by caa178c1. The block for
`set_inverse_instance` should also be passed to join dependency.

Fixes #30402.

Add paths to docs for Active Storage

Address `test_after_save_callback_with_autosave` failure

when other `AutomaticInverseFindingTests` load `:comments` fixture
but does not load `:posts`.

Refer #30385 for similar issue

Refactor `SchemaDumper` to make it possible to adapter specific customization

Fix indentation [ci skip]

Update active_support_core_extensions.md [ci skip]

Update azure-core to 0.1.11 to fix rails-dev-box

[ci skip]Revert commits changing wrong place

rails-dev-box was failing to install gems with a filesystem permission
error. The issue was introduced when azure-core was bumped from 0.1.9 to
0.1.10 in d2f493c7. azure-core has fixed the build problem [1] and
released a new version, 0.1.11 with the fix.

This change is just to run `bundle update azure-core` to pick up that
fix.

[1]: https://github.com/Azure/azure-ruby-asm-core/commit/536c3fc21cc48c292959cc10a9e5551e165aa0ed

Remove `alt` text from `image_tag` example [ci skip]

This reverts commits 5147ab12 and 391043ab.

These commits looked to intend to change documents of has_many dependent options, but actually changed documents of belongs_to dependent options.

Follow up of #30213

Fix broken link for Java xml [ci skip]

Use REDIS_URL var for Action Cable config template