The only thing I am aware of is a configurable regular expression in Gitlab CI to gather test converage data. ONE SINGLE DATA POINT. That’s all I see.
Looking in the issue tracker I see requests for more:
For now any data you want has to be generated by your own internal scripts, and then stored somewhere, and then exported using the artifacts system, or you can write code which from your CI task, actually does some HTTP posts of its own to write its results somewhere.
As far as a client side reporting tool for Git, I would only want such a tool to actually run on my gitlab server (as some service or daemon on that service) since where I work the source of Truth is whatever central/root/upstream repo and master branch on gitlab is really the “trunk”.