After an unfortunate incident involving "R --slave > analysis.r" rather than "R --slave < analysis.r", I've added the following to my .emacs:
(add-hook 'after-save-hook '(lambda ()
(if (vc-git-registered (buffer-file-name))
(vc-git-checkin (buffer-file-name) nil (format-time-string "Autocommit %F %T")))))
Such that if I'm in a git repo, every save gets committed. So, I'll need to find a new stupid mistake to destroy my work.
I also learned that a list of unpushed commits can be viewed with "git log origin/master..HEAD".
Update: See Autocommit II for an improved version.