Introduce a common data type for less-than / equal / greater-than com…

…parisons. (#128)

lib/xgit/core/dir_cache.ex

@@ -23,6 +23,8 @@ defmodule Xgit.Core.DirCache do
   use Bitwise
   use Xgit.Core.FileMode
 
+  alias Xgit.Util.Comparison
+
   @typedoc ~S"""
   Version number for an index file.
   """
@@ -200,7 +202,7 @@ defmodule Xgit.Core.DirCache do
     * `:eq` if they are the same.
     * `:gt` if `entry1` sorts after `entry2`.
     """
-    @spec compare(entry1 :: t | nil, entry2 :: t) :: :lt | :eq | :gt
+    @spec compare(entry1 :: t | nil, entry2 :: t) :: Comparison.result()
     def compare(entry1, entry2)
 
     def compare(nil, _entry2), do: :lt

lib/xgit/util/comparison.ex

@@ -0,0 +1,10 @@
+defmodule Xgit.Util.Comparison do
+  @moduledoc ~S"""
+  Common vocabulary for data types that can be compared and/or sorted.
+  """
+
+  @typedoc """
+  Result of a comparison.
+  """
+  @type result :: :lt | :eq | :gt
+end

lib/xgit/util/paths.ex

@@ -50,11 +50,9 @@ defmodule Xgit.Util.Paths do
   """
 
   use Bitwise
-
   use Xgit.Core.FileMode
 
-  @typedoc "Comparison result."
-  @type comparison_result :: :lt | :eq | :gt
+  alias Xgit.Util.Comparison
 
   @doc ~S"""
   Remove trailing `/` if present.
@@ -87,7 +85,7 @@ defmodule Xgit.Util.Paths do
           mode1 :: FileMode.t(),
           path2 :: charlist,
           mode2 :: FileMode.t()
-        ) :: comparison_result
+        ) :: Comparison.result()
   def compare(path1, mode1, path2, mode2)
       when is_list(path1) and is_file_mode(mode1) and is_list(path2) and is_file_mode(mode2) do
     case core_compare(path1, mode1, path2, mode2) do
@@ -127,7 +125,7 @@ defmodule Xgit.Util.Paths do
   one of the other return values.
   """
   @spec compare_same_name(path1 :: charlist, path2 :: charlist, mode2 :: FileMode.t()) ::
-          comparison_result
+          Comparison.result()
   def compare_same_name(path1, path2, mode2),
     do: core_compare(path1, FileMode.tree(), path2, mode2)