Doesn't even seem to require Git repo to be published. Assume it just creates its own git repo based on actual contents of gems published on https://rubygems.org/

Example: Couldn't even find git repo for this: https://rubygems.org/gems/xkeys/versions/2.2.0 but it still has diff: https://my.diffend.io/gems/xkeys/prev/2.2.0

first sighting: diffend.io