[RFC] Add a simpler pacboy alternative for installing mingw packages

[lazka]

With the goal to have a build matrix where you only vary MSYSTEM and the rest of the config is the same, one either needs to also specify the package prefix or use the pacboy option.

I was wondering if we could provide an additional action option like "msystem_install" which takes a list of packages and just prefixes them with "$MINGW_PACKAGE_PREFIX", merging them with the existing "install" option. In case of "MSYS" it would be the same as "install". It might be easier to understand and doesn't require an extra tool to know about.

    - uses: msys2/setup-msys2@v2
      with:
        msystem: UCRT64
        install: git make
        msystem_install: openssl curl

Another option might be to have some templating and do something like install: git @MINGW_PACKAGE_PREFIX@-openssl. But I'm worried that with env vars, github/matrix vars, another "variable" type specific to this action might add more confusion.

[Biswa96]

What would be the difference with pacboy option?

[lazka]

What would be the difference with pacboy option?

Not much. That it only supports the equivalent to "name:p" and that you don't have to know about pacboy and that it can be explained in one sentence.

[Biswa96]

Does not pacboy now accept package name without :p suffix in proper MSYSTEMs?

[lazka]

Ah, yeah, true.