Pathname#relative_path_from

# File tmp/rubies/ruby-3.4.1/ext/pathname/lib/pathname.rb, line 517
def relative_path_from(base_directory)
  base_directory = Pathname.new(base_directory) unless base_directory.is_a? Pathname
  dest_directory = self.cleanpath.to_s
  base_directory = base_directory.cleanpath.to_s
  dest_prefix = dest_directory
  dest_names = []
  while r = chop_basename(dest_prefix)
    dest_prefix, basename = r
    dest_names.unshift basename if basename != '.'
  end
  base_prefix = base_directory
  base_names = []
  while r = chop_basename(base_prefix)
    base_prefix, basename = r
    base_names.unshift basename if basename != '.'
  end
  unless SAME_PATHS[dest_prefix, base_prefix]
    raise ArgumentError, "different prefix: #{dest_prefix.inspect} and #{base_directory.inspect}"
  end
  while !dest_names.empty? &&
        !base_names.empty? &&
        SAME_PATHS[dest_names.first, base_names.first]
    dest_names.shift
    base_names.shift
  end
  if base_names.include? '..'
    raise ArgumentError, "base_directory has ..: #{base_directory.inspect}"
  end
  base_names.fill('..')
  relpath_names = base_names + dest_names
  if relpath_names.empty?
    Pathname.new('.')
  else
    Pathname.new(File.join(*relpath_names))
  end
end