title: unknown option `allow-unrelated-histories'
body: <p>I have two repos: Market and Android. When I merge Android to Market use these steps:</p>
  
  <pre><code>cd market
  git remote add android ../android
  git fetch android
  git merge --allow-unrelated-histories android/master
  </code></pre>
  
  <p>But I get this error:</p>
  
  <blockquote>
    <p>ei@localhost:~/market$ git merge --allow-unrelated-histories
    android/master error: unknown option `allow-unrelated-histories'</p>
  </blockquote>
  
  <p>My enviroment: Ubuntu LTS 14.04</p>
  
  <pre><code>ei@localhost:~/market$ git --version
  git version 1.9.1
  </code></pre>
  
  <p>Is this option removed from Git merge, or do I need some extra config?</p>
  
  <p>Any help would be appreciated, thanks!</p>