check std feature against kv_unstable

[KodrAus]

Closes #433

There's an incorrect #[cfg(feature = "std")] in kv::value that's broken users upgrading to 0.4.12. This PR fixes that up and runs a few more permutations in CI.

[KodrAus]

It looks like this slipped through because the feature mismatch was masked by dev dependencies.

[Byron]

Thanks a lot for the quick fix! I was just investigating why smol fails to compile (and probably many more).

[KodrAus]

Once CI goes through I'll publish a 0.4.13 version. In the meantime 0.4.12 has been yanked.

[Byron]

Thanks so much - another cargo update later and the world is fixed :).

[Byron]

Thinking about it - in case you believe this could possibly happen again, then cargo all-features might be the tool to enforce testing all permutations automatically.

[KodrAus]

It's definitely something worth looking into! We do something like this over in env_logger. One of the challenges here is that the dependencies whose features we were misusing also appear as dev-dependencies, which is why permutations of feature flags in tests didn't pick this up. So now we check them in nightly using the unstable avoid-dev-deps flag.

[Byron]

Even though I don't truly follow 😅 I would like to point out that the tool can be configured with options to handle special cases better. It seems this feature was entirely contributed, so I would hope that other needs that log might have could be contributed there as well.

[KodrAus]

Ah great I'll take a look! If cargo-check-all-features passes through our additional -Z avoid-dev-deps args then that should be everything we need.