[MPLUGIN-92] helpmojo resulting mojo requires a project and performs multiple times

Submitted by: Raphaël Piéroni
Reviewed by: Benjamin Bentmann

o Omitted @aggregator from patch which is implied by @requiresProject=false

git-svn-id: https://svn.apache.org/repos/asf/maven/plugin-tools/trunk@654751 13f79535-47bb-0310-9956-ffa450edef68

maven-plugin-tools-api/src/main/java/org/apache/maven/tools/plugin/generator/PluginHelpGenerator.java

@@ -254,6 +254,7 @@ public class PluginHelpGenerator
         writer.write( " *" + LS );
         writer.write( " * @version generated on " + new Date() + LS );
         writer.write( " * @goal " + getHelpGoalName() + LS );
+        writer.write( " * @requiresProject false" + LS );
         writer.write( " */" + LS );
     }