When a github link to a “different than master” branch is posted, the onebox should somehow show the branch name.
Here is an exmaple from Proposal: Consolidated Review Queue - #8 by eviltrout :
From this preview i understand that this is on github.com/discourse/discourse and i would expect the branch to be the master branch, which is not correct as the branch is named reviewable: https://github.com/discourse/discourse/tree/reviewable. (Also observe that in the inline link, the branch name is shown correctly).