!!rebaseme: Disable git merge.ff so merges always commit.

!!rebaseme: Committed from GitHub because the stupid Windows proxy here doesn't let Git access the Internet. Reformat this commit log...

This way when I explicitly want to track a merge it is always tracked as such, even if it introduces no new changes (i.e., fast-forward). To fast-forward one can still use git-merge --ff when it's actually desirable. Otherwise, rebase is probably what you want anyway.