Python 3 compat fixes

Specifically "string_escape" does not exist as an encoding anymore.

Author: nvie

git/diff.py

@@ -27,7 +27,10 @@ def decode_path(path, has_ab_prefix=True):
         return None
 
     if path.startswith(b'"') and path.endswith(b'"'):
-        path = path[1:-1].decode('string_escape')
+        path = (path[1:-1].replace(b'\\n', b'\n')
+                          .replace(b'\\t', b'\t')
+                          .replace(b'\\"', b'"')
+                          .replace(b'\\\\', b'\\'))
 
     if has_ab_prefix:
         assert path.startswith(b'a/') or path.startswith(b'b/')

git/test/test_diff.py

@@ -158,7 +158,7 @@ def test_diff_unsafe_paths(self):
         self.assertEqual(res[5].b_path, u'path/with\nnewline')
         self.assertEqual(res[6].b_path, u'path/with spaces')
         self.assertEqual(res[7].b_path, u'path/with-question-mark?')
-        self.assertEqual(res[8].b_path, ur'path/¯\_(ツ)_|¯')
+        self.assertEqual(res[8].b_path, u'path/¯\\_(ツ)_|¯')
 
         # The "Moves"
         # NOTE: The path prefixes a/ and b/ here are legit!  We're actually