title: Phabricator: how to make arc diff ignore untracked files and how to edit reviewers
body: <p>I recently set up Phabricator for my team, and I have two questions regarding to "arc" behavior.</p>
  
  <ol>
  <li><p>When I want to send a review, I do
  git add 
  git commit
  arc diff 
  now, if I have untracked files, arc will not let me do it unless I commit those untracked files or delete them, is there a way to just let arc diff generate reviews  for what I have commited but have not pushed.</p></li>
  <li><p>When I successfully proceed with 'arc diff', it ask me to fill up "test plan", which is fine, and "reviewers"... which is troublesome in my opinion, because of two reasons: (1), I don't know what format of the person is expected, and I don't know how to spell some of the names (2) When I need 10 people to review my code, I need to write ten names. Is there a way I can leave this blank first, and then go to phabricator.mydomain.com to edit the reviews, and send the review request?</p></li>
  </ol>
  
  <p>Thanks</p>