title: Maven2 property that indicates the parent directory
body: <p>I have a multi-modules project, like this one:</p>
  
  <pre><code>main-project/
      module1/
      module2/
          sub-module1/
          sub-module2/
          sub-module3/
          ...
      module3/
      module4/
      ...
  </code></pre>
  
  <p>I need to define a set of properties (that are dependent of the environment on which I want to release my project) in Maven2.
  I will not use <code>&lt;properties&gt;</code> as there is lots of properties...
  Thus, I use the <a href="http://mojo.codehaus.org/properties-maven-plugin" rel="noreferrer">Properties Maven2 plugin</a>.</p>
  
  <p>The properties files are located in the <code>main-project/</code> directory.
  How can I set the correct directory in the main pom.xml, in order to specify to any children where to find the properties file?</p>
  
  <pre><code>&lt;plugin&gt;
      &lt;groupId&gt;org.codehaus.mojo&lt;/groupId&gt;
      &lt;artifactId&gt;properties-maven-plugin&lt;/artifactId&gt;
      &lt;version&gt;1.0-alpha-1&lt;/version&gt;
      &lt;executions&gt;
          &lt;execution&gt;
              &lt;phase&gt;initialize&lt;/phase&gt;
              &lt;goals&gt;
                  &lt;goal&gt;read-project-properties&lt;/goal&gt;
              &lt;/goals&gt;
              &lt;configuration&gt;
                  &lt;files&gt;
                      &lt;file&gt;???/env_${env}.properties&lt;/file&gt;
                  &lt;/files&gt;
              &lt;/configuration&gt;
          &lt;/execution&gt;
      &lt;/executions&gt;
  &lt;/plugin&gt;
  </code></pre>
  
  <p>If I set only <code>&lt;file&gt;env_${env}.properties&lt;/file&gt;</code>, then when Maven2 compiles the first module, it will not find the <code>main-project/env_dev.properties</code> file. If I set <code>&lt;file&gt;../env_${env}.properties&lt;/file&gt;</code>, then an error will be raised at the parent level, or at any sub-module level...</p>