Simplest fix here is specific to the docker manager plugin. I am not sure how I feel about running an extra git command or to go hunting for git remotes on every plugin, every time we boot.
But docker manager plugin could do that extra work and put a big red icon on official plugins that appear to be forked.
I will slot 
for the next release, so it will happen over the next 6 months or so.
pr-welcome as well if anyone wants to fiddle with docker manager.