Fix error message when invoking wrong command.

Summary: @​public

The message we were showing before didn't include correctly the commands the private cli had.

Reviewed By: @vjeux

Differential Revision: D2530164

fb-gh-sync-id: 2b00c74cb41441686587588632815c5948f3a864

private-cli/src/cli.js

@@ -61,4 +61,7 @@ function help() {
   return Promise.resolve();
 }
 
-module.exports.run = run;
+module.exports = {
+  commands: documentedCommands,
+  run: run,
+};