implement PluginExecAware to expose plugin commands

Author: rcannood

src/main/groovy/provider/plugin/TestNfCommandsPlugin.groovy

@@ -17,16 +17,24 @@
 package provider.plugin
 
 import groovy.transform.CompileStatic
+import nextflow.cli.Launcher
+import nextflow.cli.PluginExecAware
 import nextflow.plugin.BasePlugin
 import org.pf4j.PluginWrapper
 
 /**
  * The plugin entry point
  */
 @CompileStatic
-class TestNfCommandsPlugin extends BasePlugin {
+class TestNfCommandsPlugin extends BasePlugin implements PluginExecAware {
 
     TestNfCommandsPlugin(PluginWrapper wrapper) {
         super(wrapper)
     }
+
+    @Override
+    int exec(Launcher launcher, String pluginId, String cmd, List<String> args) {
+        println "Hello from test-nf-plugin-commands:${cmd}!"
+        return 0
+    }
 }