Move the NestingRulesProvider interface to public API

http://intellij-support.jetbrains.com/hc/en-us/community/posts/208573345-Is-it-OK-to-use-NestingTreeStructureProvider-

platform/lang-api/src/com/intellij/ide/projectView/NestingRulesProvider.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2000-2016 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.intellij.ide.projectView;
+
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * This interface is intended for a provider of nesting rules for the project view.
+ * Implementations of the {@link #addFileNestingRules} method should pass
+ * the longest possible file name suffix to the consumer.
+ * Usually this suffix starts with a dot. For example ".js"->".min.js".
+ * You can specify a custom provider in the {@code plugin.xml} file:<pre>
+ * &lt;extensions defaultExtensionNs="com.intellij"&gt;
+ * &nbsp;&nbsp;&nbsp;&nbsp;&lt;projectViewNestingRulesProvider implementation="my.package.MyRulesProvider"/&gt;
+ * &lt;/extensions&gt;</pre>
+ */
+public interface NestingRulesProvider {
+  void addFileNestingRules(@NotNull Consumer consumer);
+
+  interface Consumer {
+    void addNestingRule(@NotNull String parentFileSuffix, @NotNull String childFileSuffix);
+  }
+}

platform/lang-impl/src/com/intellij/ide/projectView/impl/NestingTreeStructureProvider.java

@@ -15,6 +15,7 @@
  */
 package com.intellij.ide.projectView.impl;
 
+import com.intellij.ide.projectView.NestingRulesProvider;
 import com.intellij.ide.projectView.TreeStructureProvider;
 import com.intellij.ide.projectView.ViewSettings;
 import com.intellij.ide.projectView.impl.nodes.NestingTreeNode;
@@ -46,25 +47,13 @@ import java.util.*;
  * Nesting logic is based on file names only. Rules about files that should be nested are provided by
  * <code>com.intellij.projectViewNestingRulesProvider</code> extensions.
  *
- * @see NestingTreeStructureProvider.NestingRulesProvider
+ * @see NestingRulesProvider
  */
 public class NestingTreeStructureProvider implements TreeStructureProvider, DumbAware {
 
   private static ExtensionPointName<NestingRulesProvider> EP_NAME =
     ExtensionPointName.create("com.intellij.projectViewNestingRulesProvider");
 
-  public interface NestingRulesProvider {
-    /**
-     * Implementations should pass the longest possible file name suffix to the <code>consumer</code>.
-     * Usually it starts with dot. For example ".js"->".min.js".
-     */
-    void addFileNestingRules(@NotNull final NestingRulesConsumer consumer);
-  }
-
-  public interface NestingRulesConsumer {
-    void addNestingRule(@NotNull final String parentFileSuffix, @NotNull final String childFileSuffix);
-  }
-
   private static final Logger LOG = Logger.getInstance(NestingTreeStructureProvider.class);
   private Set<NestingRule> myNestingRules;
 
@@ -76,7 +65,7 @@ public class NestingTreeStructureProvider implements TreeStructureProvider, Dumb
       final MultiMap<String, String> childToParentSuffix = new MultiMap<>();
       final MultiMap<String, String> parentToChildSuffix = new MultiMap<>();
 
-      final NestingRulesConsumer consumer = new NestingRulesConsumer() {
+      final NestingRulesProvider.Consumer consumer = new NestingRulesProvider.Consumer() {
         @Override
         public void addNestingRule(@NotNull final String parentFileSuffix, @NotNull final String childFileSuffix) {
           LOG.assertTrue(!parentFileSuffix.isEmpty() && !childFileSuffix.isEmpty(), "file suffix must not be empty");

platform/platform-resources/src/META-INF/LangExtensionPoints.xml

@@ -880,7 +880,7 @@
     </extensionPoint>
 
     <extensionPoint name="projectViewNestingRulesProvider"
-                    interface="com.intellij.ide.projectView.impl.NestingTreeStructureProvider$NestingRulesProvider"/>
+                    interface="com.intellij.ide.projectView.NestingRulesProvider"/>
   </extensionPoints>
 </idea-plugin>