Some commits adds `**` to address kwargs warnings in Ruby 2.7, but
`save` and `save!` are originally doesn't take positional arguments, so
maintain both `*` and `**` is redundant.

https://github.com/rails/rails/commit/6d68bb5f695414b1801c1c3952ef955a5b0b6c6a
https://github.com/rails/rails/commit/09d7ce79750d08b6b9c64fd038eee285d0cbfd44
https://github.com/rails/rails/commit/51a7422c9f10cc75a3ef6bf9177324fc771d7ba4

PERF: Improve performance of where when using an array of values

More concise Arel `Or` ast and make `Or` visitor non recursive

Fix `rewhere` to truly overwrite collided where clause by new where clause

```ruby
steve = Person.find_by(name: "Steve")
david = Author.find_by(name: "David")

relation = Essay.where(writer: steve)

# Before
relation.rewhere(writer: david).to_a # => []

# After
relation.rewhere(writer: david).to_a # => [david]
```

For now `rewhere` only works for truly column names, doesn't work for
alias attributes, nested conditions, associations.

To fix that, need to build new where clause first, and then get
attribute names from new where clause.

Include parallelize :threads option in template when fork not available

This is a remnant of the auto-explain feature, which was removed in
d3688e02.

Fix flakey destroyed_by_association tests

Inspect time attributes with subsec

Example failure: https://buildkite.com/rails/rails/builds/68661#84f8790a-fc9e-42ef-a7fb-5bd15a489de8/1002-1012

The failing `destroyed_by_association` tests create an author (a
DestroyByParentAuthor) and a book (a DestroyByParentBook) that belongs
to that author.  If the database already contains books that refer to
that author's ID from previous tests (i.e. tests that disabled
`use_transactional_tests`), then one of those books will be loaded and
destroyed instead of the intended DestroyByParentBook book.

By loading the `:books` fixtures, we ensure the database does not
contain such unexpected books.
Co-authored-by: NEugene Kenny <elkenny@gmail.com>
Co-authored-by: NRyuta Kamizono <kamipo@gmail.com>

before
```
p Knot.create
=> #<Knot id: 1, created_at: "2016-05-05 01:29:47">
```

after
```
p Knot.create
=> #<Knot id: 1, created_at: "2016-05-05 01:29:47.116928000">
```

Style fix for CachingKeyGenerator

Add a separator to the cache key for ActiveSupport::CachingKeyGenerator

Remove hashing from secure_compare and clarify documentation

Adds :inline option to Action Mailbox generator rails_command

Support reentrant calls to RakeCommand.perform

Rake stores the current top-level task and arguments in global state.
Invoking another top-level task within the same process requires
overwriting this state.  Doing so indiscriminately can cause incorrect
behavior, such as infinitely repeating the original task.  In
particular, this is a problem when running one task from another via
`rails_command "...", inline: true`.

The solution is to save and restore the global state in each call to
`RakeCommand.perform` using the `Rake.with_application` method.

Fixes #39128.

[ActiveStorage] Rewrite Blob.unattached scope code using where.missing

https://buildkite.com/rails/rails/builds/68645#ebd598f6-fe4c-4273-b1a9-c78055f21874/1016-1027

Allow associations to be autosaved multiple times

Since 901d62c5, associations can only be
autosaved once: after a record has been saved, `@new_record_before_save`
will always be false. This assumes that records only transition to being
persisted once, but there are two cases where it happens multiple times:
when the transaction that saved the record is rolled back, and when the
persisted record is later duplicated.

Fix `modules_for_helpers` to will raise `MissingHelperError`

Deprecate marshalling load from legacy attributes format