class Build::Files::Path

def self.shortest_path(path, root)
	path_components = Path.components(path)
	root_components = Path.components(root)
	
	# Find the common prefix:
	i = prefix_length(path_components, root_components) || 0
	
	# The difference between the root path and the required path, taking into account the common prefix:
	up = root_components.size - i
	
	components = [".."] * up + path_components[i..-1]
	
	if components.empty?
		return "."
	else
		return File.join(components)
	end
end