Make tidy::Version public

[Kat-zorn]

The tidy library in src/tools/tidy is used to implement the tidy tool, but is also used by other in-tree crates like feature-status-dump to analyze which features are defined in the project. This PR makes the Version struct public. This has the effect of being able to construct a version using Version::from_str("1.80.0").unwrap(). This can then be used to compare (via the already implemented PartialEq trait) the version where a feature was introduced against a user-provided value, rather than only against other features' versions.

I would like this change because I am working on a tool to filter features for several metrics (stability, first version, activity of tracking issue, etc) to help find abandoned features that need someone to push to stabilize them.

This is my first PR here. I hope it is welcome.

[rustbot]

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[jieyouxu]

One nit
@rustbot author

View changes since this review

[jieyouxu]

Suggestion: please add a comment here that e.g. features-status-dump is using this, otherwise it's easy to think this is a dead re-export.

[Kat-zorn]

There is currently no in-tree use of Version (as it is not yet public). features-status-dump just serialises the features to JSON and has no use for this. unstable-book-gen could use it to show when certain compiler flags were introduced, if rustc -Zhelp would print that, but currently doesn't and probably won't.

The main use for exporting Version is for the tool that I'm building, where it would allow users to filter on features introduced before/after a certain version. If you prefer to instead only re-export if there's an in-tree crate using it, I can look into making my tool an extension of features-status-dump instead, and add this change as part of that PR.

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[Kat-zorn]

@rustbot ready