By default only if less than 5% of files are modified - you can force automatic upgrade.

If more files are modified upgrade can fail or it will be unpredictable result.

If you still want to try to upgrade and understand all responsibility you can increase 5% threshold in inc/classes/BxDolInstallerUtils.php file:

define('BX_FORCE_AUTOUPDATE_MAX_CHANGED_FILES_PERCENT', 0.05);

For example to rise it up to 20%, change it to:

define('BX_FORCE_AUTOUPDATE_MAX_CHANGED_FILES_PERCENT', 0.20);