Function copy_workdir 

pub fn copy_workdir(
    source: &WorkdirRoot,
    destination: &WorkdirRoot,
    limits: &SnapshotLimits,
) -> Result<WorkdirSnapshot, SnapshotError>

Copies source into the empty destination by the walk, bounded by limits.max_bytes, and reports what it copied.

Opens nothing in source for writing. destination’s own mode and times are left as its creator set them.