[build] site: gitbox links without hb= branch?

While Reviewing some of the doc for the build-Plugin I noticed that the
gitbox links on the site largely dont work (resulting in a somewhat broken
redirect to GitHub). It looks like the artifact type tree and/or the
Branchen are not correct anymore. I would fix that but I dont know what’s
the correct Parameters are. Do I need to use a=blob file links or is a=tree
supposed to work? Do you need to specify the branch?

example Site where you see a broken link:

https://commons.apache.org/proper/commons-build-plugin/readme-md.html

Gitbox:

https://gitbox.apache.org/repos/asf?p=commons-build-plugin.git;a=tree;f=src/main/resources/commons-xdoc-templates/readme-md-template.md

result 

https://github.com/apache/commons-build-plugin/tree//src/main/resources/commons-xdoc-templates/readme-md-template.md

(Note the //)

It seems to be enough to specify hb=master, but the question is:
is this a required change or is buildplug8n repo configured wrong on gitbox, 
should gitbox default to the correct head branch automatically and
do we have only master or also main branches?

Gruss
Bernd