nixos: sound: warn about changes to defaults

[oxij]

Motivation for this change

I still think that change needs to be reverted, but if there's no will for that let's at the very least warn users about the problem that change introduced. Without this most ALSA users switching from releases before 18.03 will get sound, but won't get ALSA state save/restore. That would be very confusing.

All modules and tests that want to be completely headless disable this option explicitly. I.e. you won't see this warning unless you are affected.

Things done

• Tested to work as expected.

Please backport to 18.09.

[oxij]

Edit: turns out the brokenness was already included into 18.03 =/ Should I make a PR for 18.03 too?

[oxij]

And then I did: #46491.

[edolstra]

There is no point in including commit hashes in warnings.

[oxij]

I'm open to better suggestions. I don't like being vague like "some commit before 18.03" (which was another option I could come up with) when I can just give the hash (I like doing git show on random hashes I see mentioned in random PRs and comments), but I won't argue against writing whatever else you want if that gets the message across.

[oxij]

ping?

[mmahut]

Any updates on this pull request, please?

[stale]

Thank you for your contributions.
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[bhipple]

It looks like this was relevant to 18.03 / 18.09, which was a long time ago. Feel free to re-open if still relevant.