Merge branch 'pr/3634'

core/language/en-GB/Import.multids

@@ -18,4 +18,6 @@ Upgrader/Plugins/Suppressed/Version: Blocked plugin (due to incoming <<incoming>
 Upgrader/Plugins/Upgraded: Upgraded plugin from <<incoming>> to <<upgraded>>
 Upgrader/State/Suppressed: Blocked temporary state tiddler
 Upgrader/System/Suppressed: Blocked system tiddler
+Upgrader/System/Warning: Core module tiddler
+Upgrader/System/Alert: You are about to import a tiddler that will overwrite a core module tiddler. This is not recommended as it may make the system unstable
 Upgrader/ThemeTweaks/Created: Migrated theme tweak from <$text text=<<from>>/>

core/modules/upgraders/system.js

@@ -13,11 +13,13 @@ Upgrader module that suppresses certain system tiddlers that shouldn't be import
 "use strict";
 
 var DONT_IMPORT_LIST = ["$:/StoryList","$:/HistoryList"],
-	DONT_IMPORT_PREFIX_LIST = ["$:/temp/","$:/state/"];
+	DONT_IMPORT_PREFIX_LIST = ["$:/temp/","$:/state/"],
+	WARN_IMPORT_PREFIX_LIST = ["$:/core/modules/"];
 
 exports.upgrade = function(wiki,titles,tiddlers) {
 	var self = this,
-		messages = {};
+		messages = {},
+		showAlert = false;
 	// Check for tiddlers on our list
 	$tw.utils.each(titles,function(title) {
 		if(DONT_IMPORT_LIST.indexOf(title) !== -1) {
@@ -31,6 +33,17 @@ exports.upgrade = function(wiki,titles,tiddlers) {
 					messages[title] = $tw.language.getString("Import/Upgrader/State/Suppressed");
 				}
 			}
+			for(var t=0; t<WARN_IMPORT_PREFIX_LIST.length; t++) {
+				var prefix = WARN_IMPORT_PREFIX_LIST[t];
+				if(title.substr(0,prefix.length) === prefix) {
+					showAlert = true;
+					messages[title] = $tw.language.getString("Import/Upgrader/System/Warning");
+				}
+			}
+		}
+		if(showAlert) {
+			var logger = new $tw.utils.Logger("import");
+			logger.alert($tw.language.getString("Import/Upgrader/System/Alert"));
 		}
 	});
 	return messages;