extensionSystem: Install pending updates on startup

Now that we have a way to check for updates and download them, we
should actually apply them as well. Do this on startup before any
extensions are initialized, to make sure we don't run into any
conflicts with a previously loaded version.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/945

js/ui/extensionSystem.js

@@ -45,6 +45,7 @@ var ExtensionManager = class {
             return GLib.SOURCE_REMOVE;
         });
 
+        this._installExtensionUpdates();
         this._sessionUpdated();
     }
 
@@ -456,6 +457,21 @@ var ExtensionManager = class {
         }).forEach(extension => this.reloadExtension(extension));
     }
 
+    _installExtensionUpdates() {
+        FileUtils.collectFromDatadirs('extension-updates', true, (dir, info) => {
+            let fileType = info.get_file_type();
+            if (fileType !== Gio.FileType.DIRECTORY)
+                return;
+            let uuid = info.get_name();
+            let extensionDir = Gio.File.new_for_path(
+                GLib.build_filenamev([global.userdatadir, 'extensions', uuid]));
+
+            FileUtils.recursivelyDeleteDir(extensionDir, false);
+            FileUtils.recursivelyMoveDir(dir, extensionDir);
+            FileUtils.recursivelyDeleteDir(dir, true);
+        });
+    }
+
     _loadExtensions() {
         global.settings.connect(`changed::${ENABLED_EXTENSIONS_KEY}`,
             this._onEnabledExtensionsChanged.bind(this));