title: What is the Diff file syntax
body: <p>I am currently playing around with parsing diff files, and have yet to come across a solid documentation on diff files.</p>
  
  <p>I am especially interested in specifications. E.g. I don't really understand the lines that look like this (at the beginning of each changed code block):</p>
  
  <pre><code>@@ -296,7 +296,8 @@
  </code></pre>
  
  <p>I know they have to do with line numbers, and how much lines have changed, but I wasn't really able to figure out the details so far.</p>
  
  <p>What is the syntax of the output <code>diff</code> files (at least, the main parts)?</p>