Support executing a MSYS shell

[eine]

The shell in msys2do.cmd is set to MINGW64:

setup-msys2/msys2do.cmd

Line 3 in 11c006e

set MSYSTEM=MINGW64

Please, allow to provide this as an envvar or cli arg, so it is possible to start MSYS shells too (required to build PKGBUILD files, i.e., MSYS2 packages).

[Ecco]

Yeah, that's a great idea. We personally won't have any use for this so I don't think I'll have the time to write the corresponding code, but I'd happily merge a PR for this 😄

[eine]

What approach do you suggest?

• Remove line 3 from msys2do.cmd and tell users to set MSYSTEM=whatever.
• Or, triplicate msys2do.cmd.
• Or, take the first cli arg passed to msys2do.cmd and use it to set the envvar.

[Ecco]

That's a good question. I think I'd go for an option in the yml file:

- uses: numworks/setup-msys2@v1
  with:
    msystem: whatever

This option would simply be forwarded to the MSYSTEM environment variable (or default to MINGW64 if not set). Then msys2do would just not modify the MSYSTEM variable so this could be overriden per-command.

[eine]

I'm trying to test my changes before opening a PR, but I cannot use the action, not even numworks/setup-msys2@v1. See https://github.com/1138-4EB/setup-msys2/runs/249792370#step:2:3

@Ecco, does it work for you?

[Ecco]

Dude… you're trying to run msys2 on Ubuntu 😁

That being said, it's definitely something we could check.

[eine]

Stupid of me! Thanks a lot! I even forked this other project of yours to be sure https://github.com/1138-4EB/epsilon/runs/249816649 I seems it is getting late and my brain is starting to complain 😄 My apologies for the noise...

[Ecco]

That's allright 😄 Someone else might be bitten by this so I created #2 😄