diff --git a/pre_commit_hooks/util.py b/pre_commit_hooks/util.py
new file mode 100644
index 0000000..eedf7b6
--- /dev/null
+++ b/pre_commit_hooks/util.py
@@ -0,0 +1,11 @@
+from __future__ import absolute_import
+from __future__ import print_function
+from __future__ import unicode_literals
+
+from plumbum import local
+
+
+def added_files():
+    return set(local['git'](
+        'diff', '--staged', '--name-only', '--diff-filter', 'A',
+    ).splitlines())