Copyleft "warn" will allow a license

[lfrancke]

Describe the bug

When copyleft is set to warn (which is the default) all the precedence checks after point 3 in this list https://embarkstudios.github.io/cargo-deny/checks/licenses/index.html#evaluation-precedence will not be considered anymore because warn is treated as allow:

https://github.com/EmbarkStudios/cargo-deny/blob/main/src/licenses/mod.rs#L127-L138

                    match cfg.copyleft {
                        LintLevel::Allow => {
                            allow!(IsCopyleft);
                        }
                        LintLevel::Warn => {
                            warnings += 1;
                            allow!(IsCopyleft);
                        }
                        LintLevel::Deny => {
                            deny!(IsCopyleft);
                        }
                    }

This basically resembles this config:

[licenses]

copyleft = "warn"
default = "deny"

Expected behavior
I would expect warn to behave like neither from allow-osi-fsf-free with an additional warning message: Fall through to the next check.

In theory I'd be happy to provide a PR but I haven't looked at the code yet on how to emit a warning and continue.

Device:

• Version 0.9.1

[reivilibre]

I find it odd how, with the default config from cargo deny init, I get failures for permissive licences like MIT but only warning[accepted] for copyleft licences like MPL-2.0.

I would expect the default opinion for the tool to not take a stance on copyleft and let you specify individual licences to approve like normal.