Add export warning

Author: pjcdawkins

src/Command/Archive/ArchiveExportCommand.php

@@ -160,6 +160,12 @@ protected function execute(InputInterface $input, OutputInterface $output)
 
         $this->stdErr->writeln('');
 
+        $this->stdErr->writeln('<comment>Warning</comment>');
+        $this->stdErr->writeln('Your site may be changing data during archiving, resulting in inconsistencies.');
+        $this->stdErr->writeln('This tool is not suitable for making consistent backups (instead, see <info>' . $this->config()->get('application.executable') . ' snapshot:create</info>).');
+
+        $this->stdErr->writeln('');
+
         if (!$questionHelper->confirm('Are you sure you want to continue?')) {
             return 1;
         }