Pin clap_derive when making beta releases

[abonander]

In sqlx-cli we were pinning the previous beta release of clap via the following:

clap = "=3.0.0-beta.2"

However, because clap itself does not pin the version of clap_derive, when 3.0.0-beta.4 was released with breaking changes it made our users unable to simply run cargo install sqlx-cli as clap 3.0.0-beta.2 was pulling in clap_derive 3.0.0-beta.4 which generated incompatible code: launchbadge/sqlx#1378

I'm already working on a fix on our end, adding clap_derive = "=3.0.0-beta.2" to sqlx-cli/Cargo.toml, but I just wanted to put this out there if you're planning any more beta releases before 3.0 proper, that you should consider pinning clap_derive to the same version when importing it in clap so beta users don't have to remember to pin them both to avoid breakages.

[pksunkara]

Next time, please use the issue template.

[epage]

For those curious, this Cargo behavior came up on internals back in June but seemed to fizzxle out: https://internals.rust-lang.org/t/changing-cargo-semver-compatibility-for-pre-releases/14820/12

[pksunkara]

Oh that would actually be nice. I always hated how npm treats pre releases. Adding this to my already long list of things to focus on after clap v3