Make it possible to override values in Cargo.toml from external source

[magnusart]

Describe the problem you are trying to solve
I wish to be able to set cargo package version from an external source. Maybe I'm ignorant but I could not figure out how to do this.

My use case is to correlate artifacts built with CI to specific commits. These artifacts I typically store for a longer period of time.

Example of a custom version would be running git describe --always --dirty --abbrev=7 --tags which could result in something like 1.0.0-RC1-10-g0a51bc6 (ten commits since git tag 1.0.0-RC1 with hash g0a51bc6).

Describe the solution you'd like
I would have expected to be able to do something like println!("cargo:package-version={}", myCustomVersion); in build.rs. Being able to override values in Cargo.toml I assume is a general use case.

[Kaiser1989]

Similar to this one:
#6583

[epage]

While the title is generic, motivation and use cases are only for version. I'm going to close in favor of #6583 so we can keep all of the conversation around that in one place. If there is a reason we should reconsider this, let us know!