git format-patch without committing

Question

How can I generate the patch between HEAD and the staging area (without committing)?

e.g.

echo text > some.file
git add some.file
git format-patch (what-the-sha?)..HEAD

Do I have to commit then reset?

Answer 1

git diff --cached

should do the trick if you just want the patch diff.

If you really want all of the functionality of format-patch, though, you really should commit (after all, you want a commit message if you're submitting a patch upstream).