title: assign output of exec-maven-plugin to variable
body: <p>I want to use exec-maven-plugin to get git 'revision', so I'm using following configuration:</p>
  
  <pre><code>&lt;plugin&gt;
      &lt;groupId&gt;org.codehaus.mojo&lt;/groupId&gt;
      &lt;artifactId&gt;exec-maven-plugin&lt;/artifactId&gt;
      &lt;version&gt;1.2.1&lt;/version&gt;
      &lt;executions&gt;
          &lt;execution&gt;
              &lt;id&gt;gitVersion&lt;/id&gt;
              &lt;phase&gt;validate&lt;/phase&gt;
              &lt;goals&gt;
                  &lt;goal&gt;exec&lt;/goal&gt;
              &lt;/goals&gt;
          &lt;/execution&gt;
      &lt;/executions&gt;
      &lt;configuration&gt;
          &lt;executable&gt;git&lt;/executable&gt;
          &lt;workingDirectory&gt;./&lt;/workingDirectory&gt;
          &lt;arguments&gt;
              &lt;argument&gt;rev-list&lt;/argument&gt;
              &lt;argument&gt;master&lt;/argument&gt;
              &lt;argument&gt;--count&lt;/argument&gt;
          &lt;/arguments&gt;
      &lt;/configuration&gt;
  &lt;/plugin&gt;
  </code></pre>
  
  <p>but I hit a problem - how do I assign output to any variable available in other plugins/livecycles?</p>
  
  <p>(I was able to get it done using gmaven-plugin and executing groovy script, but I find it a bit of overkill/less elegant)</p>
  
  <p>EDIT:
  for reference, working solution in groovy:</p>
  
  <pre><code>&lt;plugin&gt;
      &lt;groupId&gt;org.codehaus.gmaven&lt;/groupId&gt;
      &lt;artifactId&gt;gmaven-plugin&lt;/artifactId&gt;
      &lt;version&gt;1.5&lt;/version&gt;
      &lt;executions&gt;
          &lt;execution&gt;
              &lt;phase&gt;validate&lt;/phase&gt;
              &lt;goals&gt;
                  &lt;goal&gt;execute&lt;/goal&gt;
              &lt;/goals&gt;
              &lt;configuration&gt;
                  &lt;providerSelection&gt;2.0&lt;/providerSelection&gt;
                  &lt;properties&gt;
                      &lt;script&gt;git rev-list master --count&lt;/script&gt;
                  &lt;/properties&gt;
                  &lt;source&gt;
                      def command = project.properties.script
                      def process = command.execute()
                      process.waitFor()
  
                      def describe = process.in.text.trim()
                      println "setting revision to: " + describe
  
                      project.properties.setProperty('gitVersion',describe)
                  &lt;/source&gt;
              &lt;/configuration&gt;
          &lt;/execution&gt;
      &lt;/executions&gt;
  &lt;/plugin&gt;
  </code></pre>