fix: show a helpful message when ganache instances is executed without a subcommand

src/packages/cli/src/args.ts

@@ -281,9 +281,17 @@ export default function (
             }
           )
           .version(false);
+      },
+      function () {
+        // this handler executes when `ganache instances` is called without a subcommand
+        const command = chalk`{hex("${TruffleColors.porsche}") ganache instances}`;
+        console.log(`Missing subcommand for ${command}.`);
+        console.log();
+        yargs.showHelp();
+        yargs.exit(1, new Error("No subcommand provided"));
       }
     )
-    .showHelpOnFail(false, "Specify -? or --help for available options")
+    .showHelpOnFail(false)
     .alias("help", "?")
     .wrap(wrapWidth)
     .version(version);