Make all (applicable) filesystem command signatures accept `...(rest)` instead of `<filename> ...(rest)`

[NotTheDr01ds]

Make all (applicable) filesystem command signatures accept `...(rest)` instead of ` ...(rest)`

from nushell.

[IanManske]

Yeah, I could get behind making the signatures more consistent and spreadable using form 2.. This could also help simplify the code and avoid bugs as #11212 highlights.

One thing to keep in mind for any PRs is that ls lists the current directory when given no args. So, there would have to be a condition to check that if the rest args are empty, then double check that call.arguments actually has no positional arguments.

[NotTheDr01ds]

As a nice alternative, perhaps change all of them to be <filenames> ...(rest) but detect if <filenames> is a list and automatically handle it if so.

[kuchta]

Regarding <filename> ...(rest) vs ...(rest) and spreading I think it should be possible to define rest command arguments in more general way that would encode varied number of arguments in one argument so that it would also be possible to generate correct and understandable syntax/usage documentation. Something like array destructuring (in nu psedo-code):

def cp [[src, ...rest, dest]: string] { ... }