Commit before freezing the headers

This shouldn't generally come up: under a standard flow, we don't start
sending until after the commit. But application code always finds a way.

Add a note on ActionController guide about 404

[ci skip]

Allow manually setting environment value

If for some reason some one is not able to set the environment from a migration this gives us an escape valve to manually set the environment for the database see https://github.com/rails/rails/pull/22967#issuecomment-170251635.

We will also fix the migration case, but this will ensure there is always a way to set the environment.

cc/ @sgrif

remove warnings from rake test

delete only unnecessary reporter

Reporter that defines its own users at the time of this process are also loaded,
to avoid them from being deleted, to delete only the specified to unnecessary reporter.

This removes the following warnings.

```
test/application/rake_test.rb:33: warning: ambiguous first argument; put parentheses or a space even after `/' operator
test/application/rake_test.rb:43: warning: ambiguous first argument; put parentheses or a space even after `/' operator
```

Extract `MySQL::{Column|TypeMetadata}` classes to the appropriate files

Pass the current locale to Inflector from the pluralize text helper.

The pluralize text helper uses the Inflector to determine the plural
form. The inflector accepts an optional parameter for the locale,
so we can pass it from the text helper to have locale-aware pluralizations
on the text helpers level.

The pluralize text helper now only accepts 2 positional arguments:
`count` and `singular`. Passing `plural` as a positional argument
is now deprecated.

Running tests with multiple line numbers

Test basic auth with symbols in password

remove mentions of legacy mysql adapter from guides

Add Example for using config_for

Update postgresql version to 9.4 for travis.

[ci skip] fix typo

Now available - https://docs.travis-ci.com/user/using-postgresql/

When running passing condition assertions in the same test the user had already
been saved at that point.

Split out so we have a not yet persisted user.

Rename condition tests to improve clarity a bit.

Mistakenly interpreted the test case as a sign that we should switch to
before_save, when the original pitch use case was intended as before_create.

Revert a3ab6ad0.

Adding `if` and `unless` support doesn't bode well if the callback to assign
a token only runs on create.

Switch to `before_save`, but keep the conditional so that no token already
assigned is overriden.

Fix the NoMethodErrors introduced in 224eddfc, when adding conditional token creation.

The model declarations but the column wasn't added to the schema.

Support :if and :unless in has_secure_token

Pass through :if and :unless options from has_secure_token to the
generated before_create callback

rake log:clear task updated 

It might be tough for readers to know why we implement `===`, and where
the Regexp in `derive_regexp` came from.

The line filter parsing added to ActiveSupport::TestCase is only half the story
to enable line filtering. The other half, of adding the patterns to the options,
is done in the Minitest plugin that Railties has.

Thus it makes more sense to have the filter in Railties with the other half and
all the line filtering tests.

Move the filter and extend Active Support in an initializer, so that when users
or `rails/all.rb` require `rails/test_unit/railtie` we can still filter by line.

match the environment variable name that actually checking and error message

- Avoided truncating all files if no ENV['LOGS'] specified
- Updated task to accept LOGS=all for truncating all files from log/ i.e. log/*log
- If no LOGS specified will truncates standard environment log files i.e. 'development,test,production'
- CHANGELOG & guide update added
- bin/setup test cases fixed

[ci skip] `automatic_inverse_of` returns `false` not `nil` (document …

The error message has become a `DISABLE_DATABASE_ENVIRONMENT_CHECK`, modified to match the error message.

ref: https://github.com/rails/rails/blob/master/activerecord/lib/active_record/migration.rb#L161

Merge pull request #22987 from prathamesh-sonpatki/add-missing-changelong-for-schema-migrations-version

Added missing CHANGELOG entry for https://github.com/rails/rails/pull/22976