Prevent state leak.
Remove redundant code.
Move cleanup into teardown, delete obsolete code.
remove unnecessary substitution for space in ActionView::Helpers#debug
Add an option to skip installation of Turbolinks
Always update counter caches in memory when adding records

Before, calling `size` would only work if it skipped the cache, and
would return a different result from the cache, but only if:

- The association was previously loaded
- Or you called size previously
- But only if the size was 0 when you called it

This ensures that the counter is appropriately updated in memory.
Formatting fix in AS changelog [ci skip]
[ci skip] doc corrected : ActiveRecord::Base.connections to ActiveRecord::Base.configurations
Merge pull request #15765 from rahul100885/master

[ci skip] doc corrected : ActiveRecord::Base.connections to ActiveRecord::Base.configurations
fix typo in test method names. [ci skip]
add `bin/rake db:purge` task to empty the current database.
Move test teardown into `ensure` block.
Merge pull request #15768 from zuhao/refactor_activesupport_concern_test

Move test teardown into `ensure` block.
Don't mess with `column_defaults` when optimistic locking is enabled
Don't save through records twice

If the through record gets created in an `after_create` hook that is
defined before the association is defined (therefore after its
`after_create` hook) get saved twice. This ensures that the through
records are created only once, regardless of the order of the hooks.
Don't include inheritance column in the through_scope_attributes
Add test cases for Migration#inverse_of
Merge pull request #15771 from sgrif/sg-stop-messing-with-column-defaults

Don't mess with `column_defaults` when optimistic locking is enabled
Use `column_defaults` in dirty for checking changed defaults

We no longer need to "init changed attributes" from the initializer,
either, as there is no longer a case where a given value would differ
from the default, but would not already be marked as changed.
Merge pull request #15775 from sgrif/sg-use-column-defaults-in-dirty

Use `column_defaults` in dirty for checking changed defaults