How to share my friend's shared post that was shared by another user/page/group?

Question

When we see a post from our Facebook friend that shares another post from someone else on Facebook, we want to reshare it.

My issue is that the share button will share the original post and not my friend's post (Facebook will omit his comment in my newly shared post).

How can I reshare my friend's post not the shared link only?

Answer 1

Update
I guess Facebook heard you because just 1 month after you posted it, it now happens by itself when you click "share" (unless you uncheck the option). Well, as long as you abide by the following rules:

1. The secondary post must be completely public.
2. The original item must be an external link and not a Facebook post.
3. You share the secondary post on a wall (yours or anyone else's) and not in a private message.

If you stray away from any of these rules, the original answer still applies.

Original answer
Officially you can't. Facebook treats it like a comment of sorts, so it's just like you can't officially share comments.

However, you can "cheat" Facebook by sharing the literal link i.e. instead of the share button, get the URL from the post's timestamp:

For example:

Hey everyone, see what my friend wrote:
http://www.facebook.com/ID_of_the_friend/posts/post_ID

It doesn't offer a preview, but it works...