http://openhatch.org/missions/git/rebase

If you haven't done *any* git missions, this page tells you to go back to the
"Creating a patch" mission. But there are two other dependencies of the rebase
mission!

I'd either continue checking the dependencies of all the prerequisite missions,
and send the user back to the first one, or *start* at the first mission in that
category, check the later ones, and return the first one the user hasn't done. I
don't know if multiple prerequisites are possible or desirable, though, so the
latter choice might not be helpful.

This would definitely cut the number of page loads per attempt at accessing a
mission they can't do yet.