title: What does the “@@…@@” meta line with at signs in svn diff or git diff mean?
body: <p>When I use <code>svn diff</code> or <code>git diff</code> it shows lines like:</p>
  
  <pre><code>@@ -1,5 +1,9 @@
  </code></pre>
  
  <p>What do they mean?</p>