> And lastly, is there a tool whereby I can "see" changes > between repos, kind of like git-diff but being able to > give URLs too?
Write it yourself. It's git-fetch + git-diff.
Or, put another way, if you think you need a special tool for working with a remote repository, you don't understand git-fetch.
Since git history is immutable, there is no difference between a remote copy and a local copy. And since fetching is harmless to your local repository, there's no problem.
If you don't want to copy the entire history, just fetch the tree rather than the commit. (Does git-fetch do that? It's a subset of its current effects, so would be an easy enough extension.)