Add more explanatory error message when not copying license files

[matthiasbeyer]

Closes #207

Does the error message look good to you?

[wolfv]

Definitely an improvement. I think we were considering to do some more "book-keeping" and make sure that each include glob matches at least one file. So that you get a warning (or error) if an include glob doesn't match any file.

What do you think about that?

[matthiasbeyer]

I think we can definitively do that, but for that I would refactor the copy_dir function into something a bit more powerful. I would think about an object that the caller crafts (builder pattern style) and then runs, returning some state object as result. API wise I would think of something like that:

let copy = CopyDir::new()
    .at_path(path)
    .with_include_glob(foo)
    .with_include_glob(bar) // or a fn that takes multiple of these
    .with_exclude_glob(baz)
    .build()?;
    
let res = copy.run()?;
let includes_matched = res.include_globs.iter().any(|ig| ig.matched());

and possibly some more functionality. This way we do not have to fiddle with returning tuples and possibly ambigious bool flags in the return value.

What do you think?

[baszalmstra]

I thinks thats a great idea!

[matthiasbeyer]

Ok, than that's what I'll do next.

Feel free to merge this as-is though, so we have the nice(r) error message in asap! 😆