setting to skip migration tests by default

* if you install owncloud via package it is not
  possible to skip migration tests
* this also allows to disable migration tests for
  an instance by default

config/config.sample.php

@@ -1195,6 +1195,15 @@ $CONFIG = array(
  */
 'debug' => false,
 
+/**
+ * Skips the migration test during upgrades
+ *
+ * If this is set to true the migration test are deactivated during upgrade.
+ * This is only recommended in installations where upgrade tests are run in
+ * advance with the same data on a test system.
+ */
+'update.skip-migration-test' => false,
+
 /**
  * This entry is just here to show a warning in case somebody copied the sample
  * configuration. DO NOT ADD THIS SWITCH TO YOUR CONFIGURATION!

core/ajax/update.php

@@ -50,6 +50,12 @@ if (OC::checkUpgrade(false)) {
 			\OC::$server->getIntegrityCodeChecker(),
 			$logger
 	);
+
+	if ($config->getSystemValue('update.skip-migration-test', false)) {
+		$eventSource->send('success', (string)$l->t('Migration tests are skipped - "update.skip-migration-test" is activated in config.php'));
+		$updater->setSimulateStepEnabled(false);
+	}
+
 	$incompatibleApps = [];
 	$disabledThirdPartyApps = [];
 

core/command/upgrade.php

@@ -99,6 +99,12 @@ class Upgrade extends Command {
 		$updateStepEnabled = true;
 		$skip3rdPartyAppsDisable = false;
 
+		if ($this->config->getSystemValue('update.skip-migration-test', false)) {
+			$output->writeln(
+				'<info>"skip-migration-test" is activated via config.php</info>'
+			);
+			$simulateStepEnabled = false;
+		}
 		if ($input->getOption('skip-migration-test')) {
 			$simulateStepEnabled = false;
 		}