Minor fixes: proper help syntax and ability to extend core exports (#1799)

Display proper syntax on help, ability to extend core exports.

Author: cstamas

maven-cli/src/main/java/org/apache/maven/cling/invoker/CommonsCliOptions.java

@@ -437,7 +437,7 @@ public void displayHelp(String command, PrintWriter pw) {
             formatter.printHelp(
                     pw,
                     width,
-                    command + " [args]",
+                    commandLineSyntax(command),
                     System.lineSeparator() + "Options:",
                     options,
                     HelpFormatter.DEFAULT_LEFT_PAD,
@@ -447,5 +447,9 @@ public void displayHelp(String command, PrintWriter pw) {
 
             pw.flush();
         }
+
+        protected String commandLineSyntax(String command) {
+            return command + " [options] [goals]";
+        }
     }
 }

maven-cli/src/main/java/org/apache/maven/cling/invoker/PlexusContainerCapsuleFactory.java

@@ -99,13 +99,10 @@ protected PlexusContainer container(C context) throws Exception {
                 .setName("maven");
         customizeContainerConfiguration(context, cc);
 
-        Set<String> exportedArtifacts = new HashSet<>(coreEntry.getExportedArtifacts());
-        Set<String> exportedPackages = new HashSet<>(coreEntry.getExportedPackages());
-        for (CoreExtensionEntry extension : extensions) {
-            exportedArtifacts.addAll(extension.getExportedArtifacts());
-            exportedPackages.addAll(extension.getExportedPackages());
-        }
-        CoreExports exports = new CoreExports(containerRealm, exportedArtifacts, exportedPackages);
+        CoreExports exports = new CoreExports(
+                containerRealm,
+                collectExportedArtifacts(coreEntry, extensions),
+                collectExportedPackages(coreEntry, extensions));
         Thread.currentThread().setContextClassLoader(containerRealm);
         DefaultPlexusContainer container = new DefaultPlexusContainer(cc, getCustomModule(context, exports));
 
@@ -153,6 +150,24 @@ protected void configure() {
         return container;
     }
 
+    protected Set<String> collectExportedArtifacts(
+            CoreExtensionEntry coreEntry, List<CoreExtensionEntry> extensionEntries) {
+        Set<String> exportedArtifacts = new HashSet<>(coreEntry.getExportedArtifacts());
+        for (CoreExtensionEntry extension : extensionEntries) {
+            exportedArtifacts.addAll(extension.getExportedArtifacts());
+        }
+        return exportedArtifacts;
+    }
+
+    protected Set<String> collectExportedPackages(
+            CoreExtensionEntry coreEntry, List<CoreExtensionEntry> extensionEntries) {
+        Set<String> exportedPackages = new HashSet<>(coreEntry.getExportedPackages());
+        for (CoreExtensionEntry extension : extensionEntries) {
+            exportedPackages.addAll(extension.getExportedPackages());
+        }
+        return exportedPackages;
+    }
+
     /**
      * Note: overriding this method should be avoided. Preferred way to replace Maven components is the "normal" way
      * where the components are on index (are annotated with JSR330 annotations and Sisu index is created) and, they

maven-cli/src/main/java/org/apache/maven/cling/invoker/mvnenc/CommonsCliEncryptOptions.java

@@ -116,5 +116,10 @@ protected void prepareOptions(org.apache.commons.cli.Options options) {
                     .desc("Should imply user answered \"yes\" to all incoming questions?")
                     .build());
         }
+
+        @Override
+        protected String commandLineSyntax(String command) {
+            return command + " [options] [goal]";
+        }
     }
 }