title: how does maven profile id use var?
body: <p>profile is:
  i use ${artifactId} as profile id.</p>
  
  <pre><code> &lt;profiles&gt;
      &lt;profile&gt;
          &lt;id&gt;${artifactId}&lt;/id&gt;
          &lt;build&gt;
              &lt;plugins&gt;
                  &lt;plugin&gt;
                      &lt;artifactId&gt;maven-assembly-plugin&lt;/artifactId&gt;
                      &lt;version&gt;2.3&lt;/version&gt;
                      &lt;configuration&gt;
                          &lt;descriptors&gt;
                              &lt;descriptor&gt;distribution.xml&lt;/descriptor&gt;
                          &lt;/descriptors&gt;
                      &lt;/configuration&gt;
                      &lt;executions&gt;
                          &lt;execution&gt;
                              &lt;id&gt;make-assembly&lt;/id&gt;
                              &lt;phase&gt;package&lt;/phase&gt;
                              &lt;goals&gt;
                                  &lt;goal&gt;single&lt;/goal&gt;
                              &lt;/goals&gt;
                          &lt;/execution&gt;
                      &lt;/executions&gt;
                  &lt;/plugin&gt;
              &lt;/plugins&gt;
          &lt;/build&gt;
      &lt;/profile&gt;
  </code></pre>
  
  <p>Running maven in shell:
  <code>mvn -U -Dmaven.test.skip=true -f pom.xml -Pabc_test clean install</code></p>
  
  <p>Then I catch an error:</p>
  
  <blockquote>
    <p>[WARNING] The requested profile "abc_test" could not be activated because it does not exist.
    Finish</p>
  </blockquote>