added a note about dirty graph not supported

git-svn-id: https://svn.apache.org/repos/asf/maven/shared/trunk@1469777 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/main/java/org/apache/maven/shared/dependency/graph/DependencyNode.java b/src/main/java/org/apache/maven/shared/dependency/graph/DependencyNode.java
index 4ae2d7a..f96371f 100644
--- a/src/main/java/org/apache/maven/shared/dependency/graph/DependencyNode.java
+++ b/src/main/java/org/apache/maven/shared/dependency/graph/DependencyNode.java
@@ -25,7 +25,9 @@
 import org.apache.maven.shared.dependency.graph.traversal.DependencyNodeVisitor;
 
 /**
- * Represents an artifact node within a Maven project's dependency graph.
+ * Represents an artifact node within a Maven project's dependency graph. Notice there is no support
+ * for ommitted nodes at the moment, only dependencies kept in the resolved dependency list are
+ * available.
  *
  * @author Hervé Boutemy
  * @since 2.0