[DX][D8] CMI: Add config_exclude functionality to core

[klonos]

Drupal contrib module merged in 8.8.x core: https://www.drupal.org/project/config_exclude

Config Exclude allows you to exclude modules and their configuration from being exported. It is an easy way for developers to enable development modules without the risk of accidentally exporting the enabled-state or their dependent config.

Respective d.org issue: https://www.drupal.org/project/drupal/issues/3077504 ...and change record (Drupal 8.8.x): https://www.drupal.org/node/3079028

Modules can be excluded from the configuration synchronization

Introduction

Some modules help with developing a drupal site but are not intended to be deployed to production.
Up to Drupal 8.8.0 developers had to rely on contrib solutions such as Config Split to separate the development configuration. But sometimes it is not necessary to share the development configuration and instead it is more important to guarantee that development modules can not be included in the configuration export. This is precisely what the lesser known Config Exclude contrib module did and its functionality is now available to everyone.

How to use the new feature

in settings.php:
$settings['config_exclude_modules'] = ['devel', 'stage_file_proxy'];

Effects

Excluded modules and all the configuration that directly and indirectly depends on them are not exported through in the tarball and through tools using the config.storage.export service to export the configuration.
When importing the configuration the excluded modules and their configuration are not removed.

It is possible to exclude required modules, which means that the exported configuration can not be imported any more.

This is an advanced feature and using it means opting out of some of the guarantees the configuration synchronisation provides.

[klonos]

...the only difference (and perhaps blocker) is that in D8 whether a module is enabled/disabled is based on what's inside core.extension.yml, whereas in Backdrop we still store this in the db (hence not exported with config).