added Twig_Loader_Filesystem::addPath()

lib/Twig/Loader/Filesystem.php

@@ -47,23 +47,33 @@ class Twig_Loader_Filesystem implements Twig_LoaderInterface
      */
     public function setPaths($paths)
     {
-        // invalidate the cache
-        $this->cache = array();
-
         if (!is_array($paths)) {
             $paths = array($paths);
         }
 
         $this->paths = array();
         foreach ($paths as $path) {
-            if (!is_dir($path)) {
-                throw new Twig_Error_Loader(sprintf('The "%s" directory does not exist.', $path));
-            }
-
-            $this->paths[] = $path;
+            $this->addPath($path);
         }
     }
 
+    /**
+     * Adds a path where templates are stored.
+     *
+     * @param string $path A path where to look for templates
+     */
+    public function addPath($path)
+    {
+        // invalidate the cache
+        $this->cache = array();
+
+        if (!is_dir($path)) {
+            throw new Twig_Error_Loader(sprintf('The "%s" directory does not exist.', $path));
+        }
+
+        $this->paths[] = $path;
+    }
+
     /**
      * Gets the source code of a template, given its name.
      *