* @return the root directory, never {@code null}
     * @throws IllegalStateException if the root directory could not be found
     * @see #getTopDirectory()
     * @see Project#getRootDirectory()
     * @see Project#isRootProject()
     */
    @Nonnull
    Path getRootDirectory();

    /**
     * Returns a proto session builder of this instance.
     */
    @Nonnull
    default Builder toBuilder() {
        try {

    }

    @Override
    public boolean isTopProject() {
        return getBasedir().equals(getSession().getTopDirectory());
    }

    @Override
    public boolean isRootProject() {
        return getBasedir().equals(getRootDirectory());
    }

    @Override
    public Path getRootDirectory() {
        return project.getRootDirectory();
    }

    @Override