Support comma separated list-files enum

[paulius-p]

There are quite a few cases were you need to provide a comma separated list of files for cli arguments or properties. So I think it would be good to be able to define it in the action, rather that doing sed.

[dorny]

Good idea. There's not much work to implement it. I will add it soon 👍

[dorny]

Actually there's an easy way how to do it in current version.

Use list-files: json and afterwards you can get coma separated list like this:
join(fromJSON(steps.filter.outputs.FILTER_NAME_files))

list-files: json - enables file listing using JSON format, still every action output is just a string
fromJSON() - will parse that string into actual JSON array
join - will concatenate array using default separator ,

Does it work for you or is there anything missing?

[paulius-p]

Sure, that's a possible workaround, though I think it would be much cleaner and less verbose if there would be an option in the action. Though it's up to you :)