Problem Description:
Sometimes I post links to github commits. Or phabricator commits. Example:
https://secure.phabricator.com/rP50d158a8c4d9180ea0987a8847187567cbf42112

Or other links. But I still have to manually copy and paste or write a link summary. A link auto expand feature would be a nice solution to avoid this extra work.

Feature Description:
For example, when linking to a github commit, it would automatically add the commit message or when linking to wikipedia, show the summary and stuff like that.

Something like this:
https://www.discourse.org/video/14/onebox_fixed2.mp4