title: Remove a single rule check from PMD in maven plugin
body: <p>I want to exclude a single PMD rule in POM, but it is not working.
  I have tried creating a pmd-exclude.xml (in the same dir as the pom.xml):</p>
  
  <pre><code>&lt;?xml version="1.0"?&gt;
  &lt;ruleset name="remove_rules"&gt;
      &lt;description&gt;Remove rules&lt;/description&gt;
      &lt;rule ref="rulesets/unnecessary.xml"&gt;
          &lt;exclude name="UselessParentheses"/&gt;
      &lt;/rule&gt;
  &lt;/ruleset&gt;
  </code></pre>
  
  <p>From <a href="http://www.ing.iac.es/~docs/external/java/pmd/howtomakearuleset.html" rel="noreferrer">http://www.ing.iac.es/~docs/external/java/pmd/howtomakearuleset.html</a> and referenced it in pom.xml:</p>
  
  <pre><code>&lt;plugin&gt;
      &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
      &lt;artifactId&gt;maven-pmd-plugin&lt;/artifactId&gt;
      &lt;version&gt;3.0.1&lt;/version&gt;
      &lt;configuration&gt;
          &lt;sourceEncoding&gt;utf-8&lt;/sourceEncoding&gt;
              &lt;rulesets&gt;
                      &lt;ruleset&gt;${pom.basedir}/pmd-exclude.xml&lt;/ruleset&gt;
              &lt;/rulesets&gt;
      &lt;/configuration&gt;
  &lt;/plugin&gt;
  </code></pre>
  
  <p>But it keeps reporting these rules.</p>
  
  <p>Also: I do not want to specify which rules it must check, as newer versions can (and will) include new ones and I do not want to check which new rules will run in every new version.</p>