prevent enabled command fallback to Python when it's run without --help

Summary:
I'm introducing a new Rust-only command implementation, and I never
want it to fall back to Python help, even if it's run without a
required option. Therefore, handle
DisplayHelpOnMissingArgumentOrSubcommand as well as DisplayHelp.

Reviewed By: fanzeyi

Differential Revision: D44560239

fbshipit-source-id: 43c418da3c980a34a11277c82bf350822b0bc71b

eden/fs/cli_rs/edenfsctl/src/main.rs

@@ -183,7 +183,8 @@ fn wrapper_main() -> Result<i32> {
             // UnknownArgument (whether or not --help was requested) and we
             // should fall back to Python.
             Err(e) => {
-                if e.kind() == clap::ErrorKind::DisplayHelp
+                if (e.kind() == clap::ErrorKind::DisplayHelp
+                    || e.kind() == clap::ErrorKind::DisplayHelpOnMissingArgumentOrSubcommand)
                     && should_use_rust_help(std::env::args(), &None).unwrap_or(false)
                 {
                     e.exit()