MDL-24723 new CLI maintenance mode

lib/setup.php

@@ -151,6 +151,26 @@ if (defined('WEB_CRON_EMULATED_CLI')) {
     }
 }
 
+// Detect CLI maintenance mode - this is useful when you need to mess with database, such as during upgrades
+if (file_exists("$CFG->dataroot/climaintenance.html")) {
+    if (!CLI_SCRIPT) {
+        @header('Content-type: text/html');
+        /// Headers to make it not cacheable and json
+        @header('Cache-Control: no-store, no-cache, must-revalidate');
+        @header('Cache-Control: post-check=0, pre-check=0', false);
+        @header('Pragma: no-cache');
+        @header('Expires: Mon, 20 Aug 1969 09:23:00 GMT');
+        @header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . ' GMT');
+        @header('Accept-Ranges: none');
+        readfile("$CFG->dataroot/climaintenance.html");
+        die;
+    } else {
+        define('CLI_MAINTENANCE', true);
+    }
+} else {
+    define('CLI_MAINTENANCE', false);
+}
+
 // Detect ajax scripts - they are similar to CLI because we can not redirect, output html, etc.
 if (!defined('AJAX_SCRIPT')) {
     define('AJAX_SCRIPT', false);