Function diff_visibility 

pub fn diff_visibility(
    file_perms: &[DrivePermission],
    current_parent_perms: &[DrivePermission],
    dest_folder_perms: &[DrivePermission],
) -> VisibilityDiff

Computes the visibility diff a move from the file’s current parent(s) to a destination folder would produce, given three already-fetched permission snapshots (see the module doc’s algorithm).