Use a macro to convert Geef.Object to :geef_object

lib/geef/blob.ex

@@ -1,5 +1,6 @@
 defmodule Geef.Blob do
   alias Geef.Object
+  import :macros, Object
 
   def lookup(repo, id) do
     case :geef_obj.lookup(repo, id) do
@@ -11,11 +12,11 @@ defmodule Geef.Blob do
   end
 
   def size(obj = Object[type: :blob]) do
-    :geef_blob.size(set_elem(obj, 0, :geef_object))
+    :geef_blob.size(rebind(obj))
   end
 
   def content(obj = Object[type: :blob]) do
-    :geef_blob.content(set_elem(obj, 0, :geef_object))
+    :geef_blob.content(rebind(obj))
   end
 
 end

lib/geef/commit.ex

@@ -1,5 +1,6 @@
 defmodule Geef.Commit do
   alias Geef.Object
+  import :macros, Object
 
   def lookup(repo, id) do
     case :geef_commit.lookup(repo, id) do
@@ -11,7 +12,7 @@ defmodule Geef.Commit do
   end
 
   def tree_id(commit = Object[type: :commit]) do
-    :geef_commit.tree_id(set_elem(commit, 0, :geef_object))
+    :geef_commit.tree_id(rebind(commit))
   end
 
 end

lib/geef/object.ex

@@ -1,5 +1,12 @@
 defrecord Geef.Object, Record.extract(:geef_object, from: "src/geef_records.hrl") do
 
+  @doc false
+  defmacro rebind(obj) do
+    quote do
+      set_elem(unquote(obj), 0, :geef_object)
+    end
+  end
+
   def lookup(repo, id) do
     case :geef_obj.lookup(repo, id) do
       {:ok, obj} ->

lib/geef/tag.ex

@@ -1,8 +1,9 @@
 defmodule Geef.Tag do
   alias Geef.Object
+  import :macros, Object
 
   def peel(tag = Object[type: :tag]) do
-    case :geef_tag.peel(set_elem(tag, 0, :geef_object)) do
+    case :geef_tag.peel(rebind(tag)) do
       {:ok, peeled} ->
         {:ok, Object.new peeled}
       error ->

lib/geef/tree.ex

@@ -4,6 +4,8 @@ defmodule Geef.Tree do
   alias Geef.Object
   alias Geef.TreeEntry
 
+  import :macros, Geef.Object
+
   def lookup(repo, id) do
     case :geef_tree.lookup(repo, id) do
       {:ok, obj} ->
@@ -14,7 +16,7 @@ defmodule Geef.Tree do
   end
 
   def get(tree = Object[type: :tree], path) do
-    case :geef_tree.get(set_elem(tree, 0, :geef_object), path) do
+    case :geef_tree.get(rebind(tree), path) do
       {:ok, entry} ->
         {:ok, TreeEntry.new entry}
       error ->