Zip-Ball building for git source
If I understand it correctly, repman extracts the metadata of all versions, but if you use a simple git repository as source (instead of GitHub for example) the Web UI will only show the latest version available (the packages.json contains all versions) and apart from packagist, it will not build dist files itself. (The ComposerPackageSynchronizer skips all versions, which do not have a dist url - which are all for git repositories given by a ssh url)
If this is something you would like to support, I could try to deliver at least a draft
Another thing, I am missing is the "required by", which Satis publishes in Package details.
It is as you wrote. We welcome such a contribution. As for "required by", you can have a look at: https://github.com/repman-io/repman/pull/426