title: Update destination directory with new files (if modified) using ant
body: <p>I'm facing a problem with ant "copy". Here is my requirement:
  I want to sync 2 dirs(dir1 and dir2) but i want to keep the extra files/dirs present in dir2. My aim is i want to copy dir1 contents(if modified ) to dir2 but want to keep any additional files/dirs present in dir2.</p>
  
  <p>I tried ant's sync task, but it is trying to keep both dirs in sync ie., it is deleting extra contents present in dir2. I don't find any flag to disable this feature:</p>
  
  <pre><code>&lt;sync todir="dir2" failonerror="true" verbose="true"&gt;                             
  &lt;fileset dir="dir1" excludes="*.svn" /&gt;
   &lt;/sync&gt;
  </code></pre>
  
  <p>I tried ant's copy with "modified" selector, but its also doing the same: :(</p>
  
  <pre><code>&lt;copy todir="dir2" failonerror="true"&gt;
    &lt;fileset dir="dir1" excludes="*.svn" &gt;                           
       &lt;modified/&gt; &lt;!-- Copies only modified files --&gt;
    &lt;/fileset&gt;
  </code></pre>
  
  <p>Can any one suggest, how can i achieve my requirement with ant?</p>