title: Apache permission for php to run `git pull`
body: <p>I'm running in trouble with my new VPS. I created a file <code>pull.php</code> with this code in my GIT folder:</p>
  
  <pre><code>&lt;?php
  $output = shell_exec('git pull');
  echo "&lt;pre&gt;$output&lt;/pre&gt;";
  ?&gt;
  </code></pre>
  
  <p>It was working fine on my shared hosting but on my VPS it's return null and no 'pull' command executed. When I change the command 'git pull' to 'git status' it's show result : </p>
  
  <blockquote>
    <p>On branch master
    Your branch is up-to-date with 'origin/master'.</p>
    
    <p>Untracked files:   (use "git add ..." to include in what will be
    committed)</p>
    
    <p>info.php    pull.php    test.txt</p>
    
    <p>nothing added to commit but untracked files present (use "git add" to
    track)</p>
  </blockquote>
  
  <p>My folder chmod to 777 and php seems can write on it properly. 'git pull' on SSH's fine. My server : Ubuntu 14.x, Apache2, php5</p>
  
  <p>I would very much appreciate any help! </p>