clap v3 - when no subcommands match, use a default?

[hardy fox]

Using clap (the derive API in v3) how can I define a subcommand variant that matches a wildcard? e.g. tmux session <my-session-name> turns into tmux session new <my-session-name>

[golden grotto]

I think to get the parser to do that you want #[clap(allow_external_subcommands)] https://docs.rs/clap/latest/clap/builder/struct.App.html#method.allow_external_subcommands

that won't direct it to a specific subcommand, just become args of the parent, though