github.com/shohhei1126/hugo@v0.42.2-0.20180623210752-3d5928889ad7/tpl/tplimpl/embedded/templates/shortcodes/gist.html

<script src="//gist.github.com/{{ index .Params 0 }}/{{ index .Params 1 }}.js{{if len .Params | eq 3 }}?file={{ index .Params 2 }}{{end}}"></script>