Use Git's patience diff algorithm for interactive add

I'd like to use Git's patience diff algorithm (the one you get if you invoke git diff with the --patience argument) with git add -p. How can I do this?

Background: I'm working with some XML files, and git diff's normal algorithm produces pretty poor diffs due to "misaligned" entry/exit tags. If I run git diff --patience, I get much more useful diffs, but there's no obvious way to use these diffs in git add -p.