Prevent user from using both required and required_unless_present

[imlazyeye]

I just filed a PR to starship to fix an issue where both required and required_unless_present were used, as showed in the code below.

/// The name of the module to be printed
#[clap(required = true, required_unless_present = "list")]
name: Option<String>,

Because required is listed, the required_unless_present does not do anything, and name is required no matter what. Am I right to assume that the combination of these two fields is always incorrect, and would it be possible to provide an error to the user if they do this?

[epage]

Yes, feel free to create an issue about this.

The main consideration I have is whether erroring would be a breaking change and if we have to wait until clap 4.0.

[imlazyeye]

thanks! made the issue here: #3660