title: Force GraphViz force align between subgraph
body: <p>I use GraphViz with the following dot file:</p>
  <pre><code>digraph &quot;Fast-forward&quot;
  {
      rankdir=LR;
      subgraph master
      {
          &quot;5c071a6b2c&quot; -&gt; &quot;968bda3251&quot;;
      }
      subgraph branch
      {
          &quot;35ee8ce6b6&quot; [color=&quot;blue&quot;] [style=&quot;filled&quot;];
          &quot;968bda3251&quot; -&gt; &quot;9754d40473&quot; [weight=0];
          &quot;9754d40473&quot; -&gt; &quot;9e59700d33&quot; -&gt; &quot;35ee8ce6b6&quot;;
      }
      subgraph c1
      {
          rankdir=LR;
          rank=&quot;same&quot;;
          &quot;remote/master/HEAD&quot; [shape=box];
          &quot;remote/master/HEAD&quot; -&gt; &quot;35ee8ce6b6&quot; [weight=0];
          oldmh [label=&quot;master/HEAD&quot;] [shape=box] [color=&quot;red&quot;] [style=&quot;filled&quot;];
          newmh [label=&quot;master/HEAD&quot;] [shape=box] [color=&quot;blue&quot;] [style=&quot;filled&quot;];
          oldmh -&gt; &quot;968bda3251&quot; [weight=0];
          newmh -&gt; &quot;35ee8ce6b6&quot; [weight=0];
      }
  }
  </code></pre>
  <p>It give me something like that:
  <img src="https://i.stack.imgur.com/J4tn1.png" alt="Bag thing" /></p>
  <p>But I want something like that:</p>
  <blockquote>
  <pre><code>                                                     white
                                                          |
                                                         \/
                       &quot;9754d40473&quot; -&gt; &quot;9e59700d33&quot; -&gt; &quot;35ee8ce6b6&quot;;
                       /                                  /\
  </code></pre>
  <p>5c071a6b2c -&gt; 968bda3251</p>
  <pre><code>             /\                                         |
                |
              red                                       blue
  </code></pre>
  </blockquote>
  <p>How can I do that?</p>
  <p>For your help,
  Thanks by advance.</p>