title: (git) diff output relative path?
body: <p>I need to get some diffs in my repo that are not relative to the base of the repo, but instead relative to a given base or given path.</p>
  
  <p>By default I get:</p>
  
  <pre><code>git diff
  diff --git a/path/to/file b/path/to/file
  index 0cc125e..9bf911e 100644
  --- a/path/to/file
  +++ b/path/to/file
  </code></pre>
  
  <p>But what I want is something like:</p>
  
  <pre><code>git diff --prefix=/new/path/to
  diff --git a/new/path/to/file b/new/path/to/file
  index 0cc125e..9bf911e 100644
  --- a/new/path/to/file
  +++ b/new/path/to/file
  </code></pre>
  
  <p>I have looked over the --relative option (not what I am looking for), the --src/dst-prefix (these can only change the "a" or "b" parts. Am I missing something basic?</p>