discussion: an option to fail git fetch if a pulled branch tip is not a fast forward of the existing remote tip?

I spent a little while this afternoon debugging an issue where an
upstream publisher had backtracked and published a branch tip which
was not a descendant of a previously published (and fetched) branch
tip. The net result was that the backtracked changes were preserved in
the downstream branch once the 2nd tip was pulled.

Now clearly the upstream developer should not have backtracked. That
said, it would have been nice if I could have easily configured my
porcelain to detect the backtracking condition. An option on git fetch
that implemented something similar to the git push check would have
made this easy to achieve.

Has any consideration been given to such an option? Is there a
well-known alternative pattern for detecting this case?

jon.