I know its issue management system has something similar implemented. From another issue, if we link to another issue (on GitHub of course) the latter will show the source from where it was linked:
However, a better example of a web site that implements that feature really well would be Wikipedia:
The reason I am looking for this: I am interested in learning about other GitHub projects that are based off a project. For e.g.
ng-annotate is a npm project (hosted on GitHub).
grunt-ng-annotate is, I believe, based on it. However, in the latter project there is a link saying ng-annotate, but it links to the npm page, which links to the first project I've mentioned.
I am interested in learning of any other projects that are based off ng-annotate.