Discourse has really great preview cards for links in general, dropping in a link on a new line (onebox previews).
Recently I’ve found, though, that Github repository links no longer have any previews (I think they had before), while linking to a specific file on Github has. For example posting https://github.com/resin-io-playground/awesome-resin-io:
You mean on Github’s? They seem to have updated their design (styling) as mentioned above, so that might cause issues extracting stuff, but iframely seems to say that at least the part they test for works? (even though I’m not sure if the extracted text/icons are the same as they were presented in the onebox before, or how the iframely test really compares to what the onebox should show)
Edit: Looking at this again, I think GitHub broke this. I could have sworn they used to provide og/oembed tags on the Repo landing page, but now it is definitely not there. Welcome to Iframely