title: The buildnumber-maven-plugin is returning UNKNOWN for the scmBranch
body: <p>The buildnumber-maven-plugin is able to get the revision number from git and according to <a href="http://mojo.codehaus.org/buildnumber-maven-plugin/usage.html" rel="noreferrer">the meager documentation provided</a> it should be providing the branch as well in the <code>${scmBranch}</code> property.  However, all I get is <code>UNKNOWN</code> for the <code>${scmBranch}</code> property.</p>
  
  <p>Is there something else I need to do to get the branch info from buildnumber-maven-plugin? </p>
  
  <p>Here are the relevant entries from my pom.xml:</p>
  
  <pre><code>&lt;plugin&gt;
      &lt;groupId&gt;org.codehaus.mojo&lt;/groupId&gt;
      &lt;artifactId&gt;buildnumber-maven-plugin&lt;/artifactId&gt;
      &lt;version&gt;1.2&lt;/version&gt;
      &lt;executions&gt;
          &lt;execution&gt;
              &lt;phase&gt;validate&lt;/phase&gt;
              &lt;goals&gt;
                  &lt;goal&gt;create&lt;/goal&gt;
              &lt;/goals&gt;
          &lt;/execution&gt;
      &lt;/executions&gt;
      &lt;configuration&gt;
          &lt;doCheck&gt;true&lt;/doCheck&gt;
          &lt;doUpdate&gt;true&lt;/doUpdate&gt;
      &lt;/configuration&gt;
  &lt;/plugin&gt;
  
  &lt;manifestEntries&gt;
      &lt;Build-Branch&gt;${scmBranch}&lt;/Build-Branch&gt;
      &lt;Build-Revision&gt;${buildNumber}&lt;/Build-Revision&gt;
      &lt;Build-Timestamp&gt;${maven.build.timestamp}&lt;/Build-Timestamp&gt;
  &lt;/manifestEntries&gt;
  </code></pre>