title: easiest way to undo one file change in svn
body: <p>Let's say I have the following situation:</p>
  
  <pre><code>myrepo/
    foo.txt
    bar.txt
    baz.txt
    quux.txt
    bingo.txt
  </code></pre>
  
  <p>In rev 419, I changed foo.txt, bar.txt, and bingo.txt.</p>
  
  <p>Now I discover an error and I would like to keep foo.txt from rev 418, but leave the changes in bar.txt and bingo.txt from rev 419 intact, so I can commit rev 420 so its foo.txt is the same as rev 418.</p>
  
  <p>How can I do this with a minimum of hassle?</p>