Drupal 8 - Migration - How to run a migration programmatically (including update and sync operations)

example.php

<?php

use Drupal\migrate\MigrateMessage;
use Drupal\migrate_tools\MigrateExecutable;

/**
 * Runs a migration.
 *
 * @param string $migration_name
 *   The name of the migration to run.
 * @param string $operation
 *   The migration operation to execute (import|update|sync).
 */
function run_migration(string $migration_name, string $operation = 'import') {
  /** @var \Drupal\migrate\Plugin\MigrationPluginManager $plugin_manager_migration */
  $plugin_manager_migration = \Drupal::service('plugin.manager.migration');
  $import_options = [];

  if ($migration = $plugin_manager_migration->createInstance($migration_name)) {
    switch ($operation) {
      case 'update':
        $migration->getIdMap()->prepareUpdate();
        $import_options['update'] = TRUE;
        break;

      case 'sync':
        $migration->set('syncSource', TRUE);
        $import_options['sync'] = TRUE;
    }

    $executable = new MigrateExecutable($migration, new MigrateMessage(), $import_options);
    $executable->import();
  }
}