If you installed this crate from the registry, the error is due to needing a package update. Once updated, it should be fixed. Meanwhile, to use the latest changes, you can:
Clone this repository and cd into it.
Install this repository using the following command:
create-gpui-app --workspace --name my-app error: unexpected argument '--workspace' found
Usage: create-gpui-app [OPTIONS]
For more information, try '--help'.