Feature suggestion: new 'git add -i' command to discard working copy changes

It's not infrequent that I want to discard changes I've made locally to
files ('git checkout file.txt') and find myself wishing that this was an
action available from the 'git add --interactive' UI; it feels like it
would fit in.

Does this sound like it would be useful? I might even be able to try my
hand at adding it if it seems like something that might be accepted
upstream and someone can point me at the places in the code to look.

Evan