system.theme.yml

theme_disable in drupal/core/includes/theme.inc

Disable a given list of themes.

theme_enable in drupal/core/includes/theme.inc

Enable a given list of themes.

UpdateContribTest::testUpdateShowDisabledThemes in drupal/core/modules/update/lib/Drupal/update/Tests/UpdateContribTest.php

Tests that disabled themes are only shown when desired.

update_prepare_d8_bootstrap in drupal/core/includes/update.inc

Performs extra steps required to bootstrap when using a Drupal 7 database.

enabled:
  stark: '0'