title: git post-update script does not work
body: <p>After editing my <a href="https://stackoverflow.com/questions/9227282/git-push-to-checkout">old question</a> a few times, I make a new one because it is a new question now.</p>
  
  <p>In <code>.git/hooks/post-update</code> I have:</p>
  
  <pre><code>echo "a" &gt;&gt; /home/pi/log
  git update-server-info
  git stash
  git merge testing &gt;&gt; /home/pi/log
  </code></pre>
  
  <p>To make an automated checkout. So I run on the client:</p>
  
  <pre><code>git push testing HEAD:testing
  </code></pre>
  
  <p>Now my <code>/home/pi/log</code> contains:</p>
  
  <pre><code>a
  Updating ae2f44b..04753a9
  Fast-forward
   application/views/main/index.php |    2 +-
   1 files changed, 1 insertions(+), 1 deletions(-)
  </code></pre>
  
  <p>But the file did not change!</p>
  
  <pre><code>$ git merge testing
  Already up-to-date.
  </code></pre>
  
  <p>If I remove the script, make the push and run <code>git stash</code>, <code>git merge testing</code> it works.</p>
  
  <p><strong>Update</strong></p>
  
  <p>For testing I changed a number in a file from 17 to 20. I can see the right file version if I run </p>
  
  <pre><code>git show application/views/main/index.php
  </code></pre>
  
  <p>but </p>
  
  <pre><code>vim application/views/main/index.php
  </code></pre>
  
  <p>Still contains the old number. But git claims the file is updated:</p>
  
  <pre><code>$ git merge testing
  Already up-to-date.
  </code></pre>