A request to link your shared post to the originally shared post has been a long requested feature with Google+.

Google+ are now enabling this feature, therefore when you see a reshared post it will include the original share link in the post as well.

If you are interested in the post and would like to follow or connect with the original sharer it will make it easier to connect with that person. The feature set up is still ongoing and might not show on your profile immediately but, it will be soon.

Happy Sharing!