title: XMLStarlet does not select anything
body: <p>I have a typical pom.xml, and want to print the groupId, artifactId and version, separated by colon. I think that <a href="http://xmlstar.sourceforge.net/">XMLStarlet</a> is the right tool for that. I tried several ways, but I always get an empty line.</p>
  
  <pre><code>xml sel -t -m project -v groupId -o : -v artifactId -o : -v version pom.xml
  </code></pre>
  
  <p>Expected output: </p>
  
  <pre><code>org.something.apps:app-acct:5.4
  </code></pre>
  
  <p>Real output: empty line</p>
  
  <p>Even if I try to print just the groupId I get nothing:</p>
  
  <pre><code>xml sel -t -v project/groupId pom.xml
  </code></pre>
  
  <p>I am sure that the tool sees the elements because I can list them without problem:</p>
  
  <pre><code>xml el pom.xml
  </code></pre>
  
  <p>prints the following (correctly):</p>
  
  <pre><code>project
  project/modelVersion
  project/parent
  project/parent/groupId
  project/parent/artifactId
  project/parent/version
  project/groupId
  project/artifactId
  project/version
  project/packaging
  </code></pre>
  
  <p>What's wrong?</p>
  
  <p>Here is the cut-down version of pom.xml:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;project xmlns="http://maven.apache.org/POM/4.0.0"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
                          http://maven.apache.org/maven-v4_0_0.xsd"&gt;
  
      &lt;modelVersion&gt;4.0.0&lt;/modelVersion&gt;
  
      &lt;parent&gt;
          &lt;groupId&gt;org.something&lt;/groupId&gt;
          &lt;artifactId&gt;base&lt;/artifactId&gt;
          &lt;version&gt;1.16&lt;/version&gt;
      &lt;/parent&gt;
  
      &lt;groupId&gt;org.something.apps&lt;/groupId&gt;
      &lt;artifactId&gt;app-acct&lt;/artifactId&gt;
      &lt;version&gt;5.4&lt;/version&gt;
      &lt;packaging&gt;war&lt;/packaging&gt;
  
  &lt;/project&gt;
  </code></pre>