title: View unstaged diff from git interactive add
body: <p>I'm using Git add's interactive mode (<code>git add -i</code>) for the first time and have a question about the <code>diff</code> command it offers. By default, it shows a diff for changes I've already staged (equivalent to using <code>git diff --staged</code>). Is there a way to make it show a diff of unstaged changes? This would be really helpful for when I need to selectively add some files for staging and want to see the changes I made before adding them. I would like to do this without leaving interactive mode or having another terminal open to do a regular <code>git diff</code>.</p>