pub fn set_include_dev(&mut self, include_dev: bool) -> &mut Self {
        self.include_dev = include_dev;
        self
    }
If set to true, causes dev-dependencies of the initial set to be followed.

This does not affect transitive dependencies -- for example, a build or dev-dependency's
further dev-dependencies are never followed.

The default is true, which matches what a plain `cargo build` does.
guppy/src/graph/cargo/cargo_api.rs