Use saner parent_path? implementation and add tests

Author: doorgan

apps/common/lib/lexical/path.ex

@@ -23,13 +23,14 @@ defmodule Lexical.Path do
       iex> Lexical.Path.parent_path?("/home/user/docs", "/home/user/docs/subdir")
       false
   """
+  def parent_path?(child_path, parent_path) when byte_size(child_path) < byte_size(parent_path) do
+    false
+  end
+
   def parent_path?(child_path, parent_path) do
     normalized_child = Path.expand(child_path)
     normalized_parent = Path.expand(parent_path)
 
-    child_segments = Path.split(normalized_child)
-    parent_segments = Path.split(normalized_parent)
-
-    Enum.take(child_segments, length(parent_segments)) == parent_segments
+    String.starts_with?(normalized_child, normalized_parent)
   end
 end

apps/common/test/lexical/path_test.exs

@@ -0,0 +1,5 @@
+defmodule Lexical.PathTest do
+  use ExUnit.Case, async: true
+
+  doctest Lexical.Path
+end