Function version_reaches 

pub fn version_reaches(current: Option<&str>, warn_at: Option<&str>) -> bool

Whether a CLI at current has reached the release a deprecation starts warning at.

The gate exists because deprecated_warn_at is how an author says not yet: a declaration deprecated in next year’s release should not be shouting about it in this one.

Every uncertain case warns. A missing milestone means it is deprecated now; a version this cannot read is a spec or build problem, and answering it with silence would hide a deprecation nobody then hears about. Noise is recoverable, silence is not.