code: private long lastModifiedDepTree(long lm) {
  		long result = (defineDependencies == null && requireDependencies == null) ? lm : Math.max(lm, this.lastModifiedDep);
  		if (children != null) {
  			for (Entry<String, DepTreeNode> entry : this.children.entrySet()) {
  				result = entry.getValue().lastModifiedDepTree(result);
  			}
  		}
  		return result;
  	}
docs: Returns the most recent last modified date for all the dependencies that
  are descendants of this node, including this node.
  
  @param lm
  The most recent last modified date so far
  @return The most recent last modified date including this node and it
  descendants