Make sure we chdir back in case update dir is relative, refs #7519

src/Composer/Package/Comparer/Comparer.php

@@ -70,6 +70,7 @@ class Comparer
         if (!is_array($source)) {
             return;
         }
+        chdir($currentDirectory);
         chdir($this->update);
         $destination = $this->doTree('.', $destination);
         if (!is_array($destination)) {