Function supports 

pub fn supports(version: &str) -> bool

Whether this build reads a document stamped version.

A document loads when it shares this build’s lineage: the major version once it reaches 1, and the major and minor pair while the major is 0, which is what cargo and Pkg already mean by a 0.x bump. A version this function cannot parse as semver never loads.

One lineage crosses a major boundary: a 1.x build also reads a 0.9 document, because 0.9.0 shipped the formats 1.0 freezes. Nothing else crosses, and 2.0 reads neither.