devkit: added (internal) action to show help page by its ID

It may be useful e.g. to check help IDs before adding them to the code.

plugins/devkit/resources/META-INF/plugin.xml

@@ -243,6 +243,9 @@
       <action internal="true" class="org.jetbrains.idea.devkit.dom.generator.GenerateDomModelAction" text="Generate DOM Model..."
               id="GenerateDomModel"/>
 
+      <action internal="true" class="org.jetbrains.idea.devkit.actions.ShowHelpPageByIdAction" text="Show Help Page by ID"
+              id="ShowHelpPageById"/>
+
       <add-to-group group-id="Internal" anchor="last"/>
 
     </group>

plugins/devkit/src/actions/ShowHelpPageByIdAction.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2000-2017 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 org.jetbrains.idea.devkit.actions;
+
+import com.intellij.openapi.actionSystem.AnActionEvent;
+import com.intellij.openapi.help.HelpManager;
+import com.intellij.openapi.project.DumbAwareAction;
+import com.intellij.openapi.ui.Messages;
+
+/**
+ * @author nik
+ */
+public class ShowHelpPageByIdAction extends DumbAwareAction {
+  @Override
+  public void actionPerformed(AnActionEvent e) {
+    String helpId = Messages.showInputDialog(e.getProject(), "Enter Help ID:", "Show Help Page", null);
+    if (helpId != null) {
+      HelpManager.getInstance().invokeHelp(helpId);
+    }
+  }
+}