Oh, and of course do not forget to commit the repository after the submodule head has been reset:
<code>
cd yii
&#35; goto inside the submodule directory
git reset --hard refs/tags/1.1.13
&#35; Set submodule to track the tag 1.1.13
git add .
git commit -m 'yii submodule has been changed to track release 1.1.13'
</code>