Feature request: git commit -A

Hi all- I work on the education team at GitHub and do a fair number of Git workshops. One thing that I've always found difficult to explain to newbies is how the staging area works, and why it's useful. As a hand-wave to simplify things, I usually have them use

git add -A git commit -m "..."

to not really have to worry about untracked vs. modified/removed files aren't included with `git commit -a` or `git add .`. I would like to add a `-A` flag to the `commit` command, which effectively does a `git add -A` before committing.

I was trying to submit a patch myself, but couldn't even manage to find where the various flags are defined :-) Does the feature sound reasonable? Mind pointing me in the right direction of where this would be added?

Thanks! -Aidan Feldman