Add debug log about file changed while we backed it up

Author: helmo

server/lib/classes/backup.inc.php

@@ -1995,6 +1995,9 @@ protected static function make_web_backup($web_domain, $backup_job)
                         $web_path, $backup_repos_path . '::' . $web_backup_archive
                     );
                     // Exit code 1 means a file changed during backup, not ideal but not a failure either.
+                    if ($app->system->last_exec_retcode() == 1) {
+                        $app->log('Backup of web files for domain ' . $web_domain['domain'] . ' using path ' . $web_path . ' mentined file changed while we backed it up.', LOGLEVEL_DEBUG);
+                    }
                     $success = $app->system->last_exec_retcode() == 0 || $app->system->last_exec_retcode() == 1;
             }