diff --git a/lib/linguist/repository.rb b/lib/linguist/repository.rb
index f2bcb785..1f9e09c4 100644
--- a/lib/linguist/repository.rb
+++ b/lib/linguist/repository.rb
@@ -110,22 +110,30 @@ module Linguist
         if @old_commit_oid == @commit_oid
           @old_stats
         else
-          compute_stats(@old_commit_oid, @commit_oid, @old_stats)
+          compute_stats(@old_commit_oid, @old_stats)
         end
       end
     end
 
+    def read_index
+      attr_index = Rugged::Index.new
+      attr_index.read_tree(current_tree)
+      repository.index = attr_index
+    end
+
+    def current_tree
+      @tree ||= Rugged::Commit.lookup(repository, @commit_oid).tree
+    end
+
     protected
-    def compute_stats(old_commit_oid, commit_oid, cache = nil)
+
+    def compute_stats(old_commit_oid, cache = nil)
       file_map = cache ? cache.dup : {}
       old_tree = old_commit_oid && Rugged::Commit.lookup(repository, old_commit_oid).tree
-      new_tree = Rugged::Commit.lookup(repository, commit_oid).tree
 
-      diff = Rugged::Tree.diff(repository, old_tree, new_tree)
+      read_index
 
-      attr_index = Rugged::Index.new
-      attr_index.read_tree(new_tree)
-      repository.index = attr_index
+      diff = Rugged::Tree.diff(repository, old_tree, current_tree)
 
       diff.each_delta do |delta|
         old = delta.old_file[:path]
diff --git a/test/test_repository.rb b/test/test_repository.rb
index 3401d655..13155796 100644
--- a/test/test_repository.rb
+++ b/test/test_repository.rb
@@ -68,51 +68,33 @@ class TestRepository < Test::Unit::TestCase
     assert !repo.breakdown_by_file["Ruby"].empty?
   end
 
-
   def test_linguist_override_generated?
     attr_commit = 'b533b682d5d4012ca42f4fc998b45169ec41fe33'
+    linguist_repo(attr_commit).read_index
 
     file = Linguist::LazyBlob.new(rugged_repository, attr_commit, 'Rakefile')
 
-    git_attrs = { "linguist-language" => nil,
-                  "linguist-vendored" => nil,
-                  "linguist-generated"=> true }
-
-    # TODO: get rid of this (would like this to come from git data)
-    file.stubs(:git_attributes).returns(git_attrs)
-
     # overridden in .gitattributes
     assert file.generated?
   end
 
   def test_linguist_override_vendored?
     attr_commit = 'b533b682d5d4012ca42f4fc998b45169ec41fe33'
+    repo = linguist_repo(attr_commit).read_index
+
     override_vendored = Linguist::LazyBlob.new(rugged_repository, attr_commit, 'Gemfile')
 
-    git_attrs = { "linguist-language" => nil,
-                  "linguist-vendored" => true,
-                  "linguist-generated"=> nil }
-
-    # TODO: get rid of this (would like this to come from git data)
-    override_vendored.stubs(:git_attributes).returns(git_attrs)
-
     # overridden .gitattributes
     assert override_vendored.vendored?
   end
 
   def test_linguist_override_unvendored?
     attr_commit = 'b533b682d5d4012ca42f4fc998b45169ec41fe33'
+    repo = linguist_repo(attr_commit).read_index
 
     # lib/linguist/vendor.yml defines this as vendored.
     override_unvendored = Linguist::LazyBlob.new(rugged_repository, attr_commit, 'test/fixtures/foo.rb')
 
-    git_attrs = { "linguist-language" => nil,
-                  "linguist-vendored" => "false",
-                  "linguist-generated"=> nil }
-
-    # TODO: get rid of this (would like this to come from git data)
-    override_unvendored.stubs(:git_attributes).returns(git_attrs)
-
     # overridden .gitattributes
     assert !override_unvendored.vendored?
   end