Support PureScript's --exclude-files CLI arg

[JordanMartinez]

[email protected] allows one to exclude files from compiler input via the --exclude-files argument.

-x,--exclude-files ARG   Glob of .purs files to exclude from the supplied files.

How should this flag be supported given that we currently make the following assumptions:

• a given package always contains its files in src/**/*.purs
• a given package's test (if it exists) always exists in test/**/*.purs

AFAICT, the purpose of the --exclude-files is to allow one to have multiple packages within the same src directory.

[JordanMartinez]

Seems related to purescript/registry-dev#594

[f-f]

Why would we want to support this?

Spago has a specific idea of what a package is, and that does not play well with "splitting a src directory between multiple packages"

[f-f]

And I mentioned colocation in our chat earlier today - I think I got confused, doesn't seem related

[f-f]

Me and Jordan had a call earlier today and agreed that we won't support this unless we have a good usecase