git commit --amend safety check?

We keep seeing reports of Gerrit Code Review users who incorrectly do something like:

  git clone URL foo
  cd foo
  git commit --amend -m "My first change!" -a
  git push URL HEAD:refs/for/master

Step #3 is where they get into trouble. They just amended the published tip commit and pushed it back to the server. That is... lets just say not good.

Hg is known to be more user friendly. One way its user friendly is it by default refuses to let you amend a change set that the client has reasonable assertion to believe was already published through a remote repository.

For Git that would mean `commit --amend` refusing to amend (by default) if the commit is reachable from a refs/remotes/... tracking branch.

Thoughts?