title: TAR file format issue
body: <p>It is unclear to me, what is a correct <code>.tar</code> file format, as I am experiencing proper functionality with three scenarios <em>(see below)</em>.</p>
  
  <p>Based on <code>.tar</code> specification I have been working with, the <code>magic</code> field (ustar) is null-terminated character string and <code>version</code> field is octal number with no trailing nulls. </p>
  
  <p>However I've review several <code>.tar</code> files I found on my server and I found different implementation of <code>magic</code> and <code>version</code> field and all three of them seems to work properly, probably because system ignore those fields.</p>
  
  <p>See different (3) bytes between words <strong>ustar</strong> and <strong>root</strong> in the following examples >></p>
  
  <p>Scenario 1 (<code>20 20 00</code>):</p>
  
  <pre><code> 000000F0      00 00 00 00 | 00 00 00 00 | 00 00 00 00      ............
   000000FC      00 00 00 00 | 00 75 73 74 | 61 72 20 20      .....ustar  
   00000108      00 72 6F 6F | 74 00 00 00 | 00 00 00 00      .root.......
   00000114      00 00 00 00 | 00 00 00 00 | 00 00 00 00      ............
  </code></pre>
  
  <p>Scenario 2 (<code>00 20 20</code>):</p>
  
  <pre><code> 000000F0      00 00 00 00 | 00 00 00 00 | 00 00 00 00      ............
   000000FC      00 00 00 00 | 00 75 73 74 | 61 72 00 20      .....ustar. 
   00000108      20 72 6F 6F | 74 00 00 00 | 00 00 00 00      root.......
   00000114      00 00 00 00 | 00 00 00 00 | 00 00 00 00      ............
  </code></pre>
  
  <p>Scenario 3 (<code>00 00 00</code>):</p>
  
  <pre><code> 000000F0      00 00 00 00 | 00 00 00 00 | 00 00 00 00      ............
   000000FC      00 00 00 00 | 00 75 73 74 | 61 72 00 00      .....ustar..
   00000108      00 72 6F 6F | 74 00 00 00 | 00 00 00 00      .root.......
   00000114      00 00 00 00 | 00 00 00 00 | 00 00 00 00      ............
  </code></pre>
  
  <p>Which one is the correct format?</p>