title: Git difftool with beyond compare
body: <p>I am trying to compare two git branches.
  With git I would do</p>
  
  <pre><code>git diff banch1..branch2
  </code></pre>
  
  <p>With the Beyond Compare tool I tried </p>
  
  <pre><code>git difftool branch1..branch2
  </code></pre>
  
  <p>but now it looks like it's comparing the branches file by file. So I added the <code>--dir-diff (-d)</code> flag</p>
  
  <pre><code>git difftool -d branch1..branch2
  </code></pre>
  
  <p>but now I get an error</p>
  
  <pre><code>fatal: could not open '/var/folders/zj/btt2_b5d6_b34fndcvzws9jr0000gn/T//git-difftool.VtceWd/left/ED/Template/sun-lncc/Template/dbged' for writing: No such file or directory
  </code></pre>
  
  <p>How do I fix this?</p>