Originally I tried to add `assert_equal pk.sql_type, ref.sql_type`. But
the assert failed even though the same type due to `sql_type` of primary
key in SQLite is upper case. Prefer lower case like other types.

Fix `add_column` with :primary_key type compatibility for SQLite

`invoke_all` cause `bundle install`. This will install gems actually
defined in `Gemfile`. To avoid this, stubbed `bundle_command`.

Fixes #31557

Prevent shadowing outer variables

And prefer `assert_same` over `assert_equal`.

Try to update rubygems 2.7.4

save attributes changed by callbacks after update_attribute

Puma gets bundler's info from `Bundler::ORIGINAL_ENV` for restart.
https://github.com/puma/puma/blob/f6f3892f4d82638fb7a2a57d993641b1486ee88a/lib/puma/launcher.rb#L168

So, specified `BUNDLE_GEMFILE` env for use same Gemfile in the restart.

Fixes #31351

`skip_bundle` option was removed from plugin generator in 9b72fcc3.

Fixes #31531
Closes #31540

[docs] Add mention of removal of HWIA interface from `AC:Parameters`

[ci skip]

For pass Active Job integration tests with Ruby 2.5.
Ref: https://github.com/collectiveidea/delayed_job/pull/996

[ci skip]

Add cloud service's links to README of Active Storage [ci skip]

Add support for combined MiniMagick transformations

This reverts commit 57f0e3d1.

Relax bundler version on Travis CI

Context: https://github.com/rails/rails/pull/29301#issuecomment-353200233

This reverts commit b106242f.

update_attribute previously stopped execution, before saving and before
running callbacks, if the record's attributes hadn't changed. [The
documentation](http://api.rubyonrails.org/classes/ActiveRecord/Persistence.html#method-i-update_attribute)
says that "Callbacks are invoked", which was not happening if the
persisted attributes hadn't changed.

Temporary disabled using rubygems 2.7.

  RubyGems 2.7 promote bundler-1.16 to default gems.
  It conflicts Travis environment and user installed bundler.

Pass options to rails_blob_url

[ci skip] Remove needless  from doc for ActiveStorage::Variant

Removes OS specific directory separator

Handle `FrozenError` if it is available

Fix Illegal parameter data type bigint for operation 'get_lock' error

This pull request handles `FrozenError` introduced by Ruby 2.5.
Refer https://bugs.ruby-lang.org/projects/ruby-trunk/repository/revisions/61131

Since `FrozenError` is a subclass of `RuntimeError` minitest used by master
branch can handle it, though it would be better to handle `FrozenError`
explicitly if possible.

`FrozenError` does not exist in Ruby 2.4 or lower, `frozen_error_class`
handles which exception is expected to be raised.

This pull request is intended to be merged to master,
then backported to `5-1-stable` to address #31508

Follow up of #31289.