site/docs/layouts/shortcodes/regref.html

{{ $base_url := "" }}
{{ if len .Params | eq 2 }}{{ $base_url = relref . (.Get 1) }}{{ end }}
{{ $name := .Get 0 }}{{ $ref := lower (index (split $name ".") 0) }}<a href="{{ $base_url }}#Reg_{{ $ref }}">{{ $name }}</a>{{- "" -}}