title: What is the use of the ant duplicate attribute
body: <p>In Ant1.8, I have a task like this :</p>
  
  <pre><code> &lt;jar destfile="@{destfile}.jar"
        duplicate="fail"
        manifest="@{srcfolder}/META-INF/MANIFEST.MF"&gt;       
      &lt;fileset dir="${build_folder}/" excludes="${test_package}/**"/&gt;
      &lt;fileset dir="@{srcfolder}"  includes="**/*.xml" /&gt;
      &lt;fileset dir="@{srcfolder}"  includes="**/*.properties" /&gt;
      &lt;fileset dir="@{srcfolder}"  includes="**/*.wsdl" /&gt;
      &lt;manifest&gt;
         &lt;attribute name="@{manifest-title}" value="@{manifest-name}"/&gt;
      &lt;/manifest&gt;
   &lt;/jar&gt;
  </code></pre>
  
  <p>What is the duplicate="fail" supposed to do? I keep getting error like this:</p>
  
  <pre><code>Duplicate file META-INF/wsdl/someWsdl.wsdl was found and the duplicate attribute is 'fail'.
  </code></pre>
  
  <p>The wsdl is supposed to be there because just before building the jar i do wsimport and compile the generated classes.</p>