Ignore path starting with _ on compose_node_name

https://github.com/salt-formulas/reclass/pull/48#issuecomment-406823623
diff --git a/README-extentions.rst b/README-extentions.rst
index 2053a2d..2bc4816 100644
--- a/README-extentions.rst
+++ b/README-extentions.rst
@@ -536,3 +536,5 @@
       ...
     staging.mysql:
       ...
+
+If the subfolder path starts with the underscore character ``_``, then the subfolder path is NOT added to the node name.
diff --git a/reclass/storage/common.py b/reclass/storage/common.py
index 7de71d0..13db7ec 100644
--- a/reclass/storage/common.py
+++ b/reclass/storage/common.py
@@ -14,6 +14,17 @@
         return relpath, name
 
     @staticmethod
+    def composed_nodes(relpath, name):
+        if relpath == '.' or relpath == '':
+            # './' is converted to None
+            return None, name
+        parts = relpath.split(os.path.sep)
+        if parts[0].startswith("_"):
+            return relpath, name
+        parts.append(name)
+        return relpath, '.'.join(parts)
+
+    @staticmethod
     def classes(relpath, name):
         if relpath == '.' or relpath == '':
             # './' is converted to None
diff --git a/reclass/storage/yaml_fs/__init__.py b/reclass/storage/yaml_fs/__init__.py
index 88f0ec4..7ed3fe4 100644
--- a/reclass/storage/yaml_fs/__init__.py
+++ b/reclass/storage/yaml_fs/__init__.py
@@ -61,7 +61,7 @@
         if nodes_uri is not None:
             self._nodes_uri = nodes_uri
             if compose_node_name:
-                self._nodes = self._enumerate_inventory(nodes_uri, NameMangler.classes)
+                self._nodes = self._enumerate_inventory(nodes_uri, NameMangler.composed_nodes)
             else:
                 self._nodes = self._enumerate_inventory(nodes_uri, NameMangler.nodes)