File f = getFileForClasspathResource("canonical-pom.xml");

        MavenProject project = getProject(f);

        // ----------------------------------------------------------------------
        // Top-level elements
        // ----------------------------------------------------------------------

        assertEquals("4.0.0", project.getModelVersion());

     * Returns a boolean indicating if the project is the top level project for
     * this reactor build.  The top level project may be different from the
     * {@code rootDirectory}, especially if a subtree of the project is being
     * built, either because Maven has been launched in a subdirectory or using
     * a {@code -f} option.
     *
     * @return {@code true} if the project is the top level project for this build
     */

     * directory pointed at by the {@code -f/--file} command line argument.
     */
    @Nonnull
    Path getTopDirectory();

    /**
     * Gets the root directory of the session, which is the root directory for the top directory project.
     *
     * @throws IllegalStateException if the root directory could not be found
     * @see #getTopDirectory()
     * @see Project#getRootDirectory()
     */
    @Nonnull

    void setDegreeOfConcurrency(int degreeOfConcurrency);

    /**
     * @return the degree of concurrency for the build.
     */
    int getDegreeOfConcurrency();

    // Recursive (really to just process the top-level POM)
    MavenExecutionRequest setRecursive(boolean recursive);

    boolean isRecursive();

    MavenExecutionRequest setPom(File pom);

    File getPom();

    // Errors

+-----+
${maven.home}
     |
     +--- maven.properties
+-----+

* Group configuration

 As far as properties go for an entire build the maven.properties could be placed at
 the top of the group but I'm not really sure how this might work. There could probably
 also be a directory for plugins.xml and maven.properties.

* Project configuration

     * filter is applied (like in Maven 3).
     * <p>
     * Supported filters:
     * <ul>
     *     <li>"h" or "h(num)" - highest version or top list of highest ones filter</li>
     *     <li>"l" or "l(num)" - lowest version or bottom list of lowest ones filter</li>
     *     <li>"s" - contextual snapshot filter</li>

          <version>3.0.0+</version>
          <description>The default goal (or phase in Maven 2) to execute when none is specified for
            the project. Note that in case of a multi-module build, only the default goal of the top-level
            project is relevant, i.e. the default goals of child modules are ignored. Since Maven 3,
            multiple goals/phases can be separated by whitespace.</description>
          <type>String</type>

        createLocalArtifact("h", "1.0");
        artifactResolver.resolveTransitively(
                Collections.singleton(g), projectArtifact, remoteRepositories(), localRepository(), null);

        // we want to see all top-level thread groups
        ThreadGroup tg = Thread.currentThread().getThreadGroup();
        while (tg.getParent() == null) {
            tg = tg.getParent();
        }