title: What does the "-c" mean in an ant exec task?
body: <p>These are two ant tasks:</p>
  
  <pre><code> &lt;target name="hg.add" &gt;
      &lt;exec dir="." executable="hg"&gt;
          &lt;arg line="add ${reports-summary}" /&gt;
      &lt;/exec&gt;
  &lt;/target&gt;
  
  
  &lt;target name="hg.add"&gt;
        &lt;exec executable="/bin/sh"&gt;
              &lt;arg value="-c"/&gt;
              &lt;arg value="hg add ${reports-summary}"/&gt;
        &lt;/exec&gt;
  &lt;/target&gt;
  </code></pre>
  
  <p>This two tasks seem to have the same function. But why the second one needs to write"/bin/sh" and "-c"?</p>