function rel(root, src, sep) {
  if(!root || !_.isString(root) || !src || !_.isString(src)) return
  let root_split = root.split(path.sep),
    src_split = src.split(path.sep)
  return _.join(_.difference(src_split, root_split), sep || '/')
}
function rel(root, src, sep) {
  if(!root || !_.isString(root) || !src || !_.isString(src)) return
  let root_split = root.split(path.sep),
    src_split = src.split(path.sep)
  return _.join(_.difference(src_split, root_split), sep || '/')
}
function rel ( root , src , sep ) { if ( ! root || ! _ . isString ( root ) || ! src || ! _ . isString ( src ) ) return let root_split = root . split ( path . sep ) , src_split = src . split ( path . sep ) return _ . join ( _ . difference ( src_split , root_split ) , sep || '/' ) }
returns rel path of src from root
returns rel path of src from root