Execute a drupal 8 migration via REPL

execute-migrate-via-repl.php

$m = \Drupal::service('plugin.manager.migration');
$mi = $m->createInstance('migration_id');
$source = $mi->getSourceConfiguration();
$source['urls'][0] = 'temporary://file.json'
$source['data_fetcher_plugin'] = 'file';
$mi->set('source', $source);
$exe = new \Drupal\migrate\MigrateExecutable($mi);
$mi->setStatus(\Drupal\migrate\Plugin\MigrationInterface::STATUS_IDLE);
$result = $exe->import();