When one database existed already, but not the other,
during setup of missing one, existing database was wiped out.

Extract default log file open operation to method

This allows customize a default log file(e.g. `reopen`) by an application.

Fixes #32211.

Especially, somehow `CHANGELOG.md` in actiontext and activestorage in
master branch had used 3 spaces indentation.

Reword the ActionDispatch::Response#content_type change [ci skip]

Fix sqlite3 collation parsing when using decimal columns.

Don't call listen with empty directory list

Fix sentence and a typo

Fixed the redundant addition of to [ci skip]

Document multiple databases in Rails

This file documents how to use multiple databases, what features are
supported, what features are coming soon, and caveats.

Do not clear deprecated initializer dependencies if using classic autoloader

If an sqlite3 table contains a decimal column behind columns with a collation
definition, then parsing the collation of all preceeding columns will fail --
the collation will be missed without notice.

Only clear cache when view paths are specified

Listen interprets an empty list of directories as "watch the current
directory". Since EventedFileUpdateChecker doesn't share these
semantics, we should not initialize listen if we end up with an empty
directory list.

Currently, `clear_cache_if_necessary` is executed even if view paths are
not set like `rails console`.
If the watcher class is `EventedFileUpdateChecker` and the watch
directories are empty, the application root directory will watch. This
is because listen uses the current directory as the default watch directory.
https://github.com/guard/listen/blob/8d85b4cd5788592799adea61af14a29bf2895d87/lib/listen/adapter/config.rb#L13

As a result, `node_modules` also watch. This cause a warning of `listen`.
Ref: https://github.com/rails/rails/pull/36377#issuecomment-498399576

Fix invalid schema dump when primary key column has a comment

Before this fix it would either generate an invalid schema, passing `comment` option twice to `create_table`, or it move the comment from primary key column to the table if table had no comment when the dump was generated.

The situation now is that a comment on primary key will be ignored (not present on schema).

Fixes #29966

Remove unnecessary require pathname from actionpack controller specs

This is a regression for #36184.

And also, add new `monotonic` argument to the last of the method
signature rather than the first.

`create_table` and `t.column` have the same named options (e.g.
`:comment`, `:primary_key`), so it should be separated table options
from column options.

Related #36373.

Avoid making extra 5 arrays in each `save`

Address occasional test_pluck_columns_with_same_name failure

```ruby
$ bundle exec rake test_postgresql
... snip ...
Failure:
CalculationsTest#test_pluck_columns_with_same_name [/home/yahonda/git/rails/activerecord/test/cases/calculations_test.rb:842]:
--- expected
+++ actual
@@ -1 +1 @@
-[["The First Topic", "The Second Topic of the day"], ["The Third Topic of the day", "The Fourth Topic of the day"]]
+[["The Third Topic of the day", "The Fourth Topic of the day"], ["The First Topic", "The Second Topic of the day"]]
```

Each `save` calls `all_timestamp_attributes_in_model` to fill timestamp
columns. Allthough the `all_timestamp_attributes_in_model` returns the
same value every time, the `all_timestamp_attributes_in_model` makes
extra 5 arrays every time.

This avoids the making extra 5 arrays by memoizing the result, it makes
`save` economical and a bit faster.

https://gist.github.com/kamipo/1ddad2235073f508637bf9a72d64bb83

Before (2a015f6c):

```
{["~/rails/activerecord/lib/active_record/timestamp.rb",
  76,
  :T_ARRAY]=>[1000, 0, 341, 0, 1, 13640],
 ["~/rails/activerecord/lib/active_record/timestamp.rb",
  64,
  :T_ARRAY]=>[1000, 0, 341, 0, 1, 13640],
 ["~/rails/activerecord/lib/active_record/timestamp.rb",
  80,
  :T_ARRAY]=>[1000, 0, 341, 0, 1, 13640],
 ["~/rails/activerecord/lib/active_record/timestamp.rb",
  68,
  :T_ARRAY]=>[1000, 0, 341, 0, 1, 13640],
 ["~/rails/activerecord/lib/active_record/timestamp.rb",
  73,
  :T_ARRAY]=>[1000, 0, 341, 0, 1, 13640]}
Warming up --------------------------------------
    User.create * 10    36.000  i/100ms
Calculating -------------------------------------
    User.create * 10    353.644  (± 7.4%) i/s -      1.764k in   5.021876s
```

After (this change):

```
{["~/rails/activerecord/lib/active_record/timestamp.rb",
  83,
  :T_ARRAY]=>[1, 0, 1, 1, 1, 40],
 ["~/rails/activerecord/lib/active_record/timestamp.rb",
  87,
  :T_ARRAY]=>[1, 0, 1, 1, 1, 40],
 ["~/rails/activerecord/lib/active_record/timestamp.rb",
  64,
  :T_ARRAY]=>[1, 1, 1, 1, 1, 0],
 ["~/rails/activerecord/lib/active_record/timestamp.rb",
  69,
  :T_ARRAY]=>[1, 1, 1, 1, 1, 0],
 ["~/rails/activerecord/lib/active_record/timestamp.rb",
  74,
  :T_ARRAY]=>[1, 1, 1, 1, 1, 0]}
Warming up --------------------------------------
    User.create * 10    37.000  i/100ms
Calculating -------------------------------------
    User.create * 10    380.063  (± 7.1%) i/s -      1.924k in   5.097917s
```

Change `ActionDispatch::Response#content_type` returning Content-Type header as it is

Since #35709, `Response#conten_type` returns only MIME type correctly.
It is a documented behavior that this method only returns MIME type, so
this change seems appropriate.
https://github.com/rails/rails/blob/39de7fac0507070e3c5f8b33fbad6fced84d97ed/actionpack/lib/action_dispatch/http/response.rb#L245-L249

But unfortunately, some users expect this method to return all
Content-Type that does not contain charset. This seems to be breaking
changes.

We can change this behavior with the deprecate cycle.
But, in that case, a method needs that include Content-Type with
additional parameters. And that method name is probably the
`content_type` seems to properly.

So I changed the new behavior to more appropriate `media_type` method.
And `Response#content_type` changed (as the method name) to return Content-Type
header as it is.

Fixes #35709.

[Rafael Mendonça França & Yuuji Yaginuma ]

Fix table comment also being applied to the primary key column

Fail parallel tests if workers exit early

Previously, if a test worker exited early, the in-flight test it was
supposed to run wasn't reported as a failure.

If all workers exited immediately, this would be reported as ex.

    Finished in 1.708349s, 39.2192 runs/s, 79.0237 assertions/s.
    67 runs, 135 assertions, 0 failures, 0 errors, 2 skips

This commit validates that all workers finish running tests by ensuring
that the queue is empty after they exit. This works because we signal
the workers to exit by pushing nil onto the queue, so that there should
be a number of items left in the queue matching potentially missed
tests.

https://buildkite.com/rails/rails/builds/61384#ad441461-87d8-4bdc-a71f-61921fe2df2e/993-1004

Remove wrong default value for `cache_versioning` in documentation of `cache_version`