Add specs for Repository#last_commit_for_path

spec/models/repository_spec.rb

@@ -12,4 +12,10 @@ describe Repository do
     it { should_not include('feature') }
     it { should_not include('fix') }
   end
+
+  describe :last_commit_for_path do
+    subject { repository.last_commit_for_path(sample_commit.id, '.gitignore').id }
+
+    it { should eq('c1acaa58bbcbc3eafe538cb8274ba387047b69f8') }
+  end
 end