Function validate 

pub fn validate(entry: &Entry, root: &Path) -> bool

Whether every dependency an entry recorded still holds.

root is the project root the recorded paths are relative to.

A dependency that cannot be read now counts as changed, whether it was recorded as present or absent. Permissions, a vanished directory, a race — none of them are grounds for trusting a cached answer, and the cost of being wrong is a recompute.