title: Using meld as difftool for git but listing all files in one window
body: <p>I want to use meld as my diff tool for git.</p>
  
  <p>If I configure my <code>.gitconfig</code> like this :</p>
  
  <pre><code>[difftool]
      prompt = false
  [diff]
      tool = meld
  </code></pre>
  
  <p>and run command : <code>$ git difftool</code><br>
  then git open a meld window for each file which have changes.</p>
  
  <p>But I want one single window with all my files in the meld list box.
  I have read a little about <code>-d</code> or <code>--dir-diff</code> option.<br>
  When I try : <code>$ git difftool -d</code><br>
  then a single windows is opened with one directory tree in each meld part, but either contain empty directories.<br>
  I can not open my files from here.</p>
  
  <p><img src="https://i.stack.imgur.com/82kaf.png" alt="enter image description here"></p>
  
  <p>For infomation :</p>
  
  <pre><code>$ git --version
  git version 1.9.1
  $ meld --version
  meld 1.8.4
  $ lsb_release -d
  Description:    Ubuntu 14.04.2 LTS
  </code></pre>
  
  <p>I am using <code>git svn</code> too, but I don't think this is related in my problem; because as far as I understand git-svn, my directory work as a simple git directory.</p>
  
  <p>Related questions  :<br>
  <a href="https://stackoverflow.com/questions/2006032/view-differences-of-branches-with-meld">View differences of branches with meld?</a></p>