Fix typo in ActiveJob #retry_job doc

Followup of #15771

Make sure we handle explicitly passed nil's to lock_version as well.
An explicitly passed nil value is now converted to 0 on LockingType,
so that we don't end up with ActiveRecord::StaleObjectError in update record
optimistic locking

Fixes #24695

Follow up of https://github.com/rails/rails/commit/c9c5788a527b70d7f9…

[ci skip]

Previously these methods could return either a DateTime or a Time
depending on how the ActiveSupport::TimeWithZone instance had
been constructed. Changing to always return an instance of Time
eliminates a possible stack level too deep error in to_time where
it was wrapping a DateTime instance.

As a consequence of this the internal time value is now always an
instance of Time in the UTC timezone, whether that's as the UTC
time directly or a representation of the local time in the timezone.

There should be no consequences of this internal change and if
there are it's a bug due to leaky abstractions.

Mirrors the Time#subsec method by returning the fraction
of the second as a Rational.

Time instances can have fractional parts smaller than a nanosecond.

Mirrors the DateTime#sec_fraction method by returning the fraction
of the second as a Rational.

Move `DateTime#getlocal` to `/core_ext/date_time/calculations.rb`

`DateTime#getlocal` is newly added public API.
It's responsible is same as `DateTime#utc`, so `calculations.rb` is
a best plase to define this method.
For keeping consistency with `DateTime#utc`, defines `#localtime` and
defines `getlocal` as an alias method.

In Ruby 2.4 the `to_time` method for both `DateTime` and `Time` will
preserve the timezone of the receiver when converting to an instance
of `Time`. Since Rails 5.0 will support Ruby 2.2, 2.3 and later we
need to introduce a compatibility layer so that apps that upgrade do
not break. New apps will have a config initializer file that defaults
to match the new Ruby 2.4 behavior going forward.

For information about the changes to Ruby see:
https://bugs.ruby-lang.org/issues/12189
https://bugs.ruby-lang.org/issues/12271

Fixes #24617.

Actionpack documentation typos [ci skip]

Re. 6e098284

Fix test name

Gracefully fallback on version migrations for sqlite < 3.7.11

https://github.com/rails/rails/commit/42dd2336b31a8d98776d039a2b9fd7f834156a78 changed INSERT INTO versions to run in 1 single query.
This breaks for sqlite versions < 3.7.11, which is especially the case on Ubuntu 12.04 LTS, that has SQLite version 3.7.9 as default.

So we check for support for multi insert, before performing single query inserts, else fallback to older version of running multiple queries.
[Vipul A M & Yasuo Honda]

When the query cache completes, if Active Record is still inside of a
transaction, it is because the transaction is meant to be left open
above this unit of work (such as transactional fixtures in tests). There
were several tests around the behavior of "tests" that were invalid, as
tests are not run through the executor. They have been changed to
reflect the new behavior, which is closer to what actually occurs in
Rails tests.

Fixes #23989
Fixes #24491
Close #24500

Slight refactor to improve boot performance on some Ruby
implementations (for now).

Fix broken links in 'Ruby on Rails 3.0 Release Notes' [ci skip]

Change definition of what async means for an Active Job Job [ci skip]

- [ci skip] Active Job Async doesn't support to Async feature as per it's definition.

- [ci skip] Active Job Async doesn't support to Async feature as per it's definition.

- [ci skip] Active Job Async doesn't support to Async feature as per it's definition.

- [ci skip] Active Job Async doesn't support to Async feature as per it's definition.

Combine inequality and equality and add SQL examples [ci skip]

Actioncable and Actionpack documentation typos [ci skip]

Further investigation seems to disprove that backtracking is the
reason why the positive variant is slower, see

    https://github.com/rails/rails/pull/24658#issuecomment-213079710

so, just say nothing about it, only assert it is slower.

using rails dev:cache instead of rake dev:cache

Log if redis connection is in stale/failed state.

Without the `wdm` gem, it appears that `listen` keeps an open handle to
each of these files, causing them not to be removed when the tempdir
tries to clean iteslf up, and then directory to fail to unlink. In
addition to fixing that particular failure, we now construct OS agnostic
paths, and capture exceptions if the directory fails to unlink so that
minitest will report it rather than crash