Skip patch tests if C git is not available, update NEWS.

NEWS

@@ -7,6 +7,9 @@
 
  * Add a basic ``porcelain.clean``. (Lane Barlow, #398)
 
+ * Fix output format of ``porcelain.diff`` to match that of
+   C Git. (Boris Feld)
+
 0.19.11	2019-02-07
 
  IMPROVEMENTS

dulwich/tests/compat/__init__.py

@@ -27,6 +27,7 @@ def test_suite():
     names = [
         'client',
         'pack',
+        'patch',
         'repository',
         'server',
         'utils',

dulwich/tests/compat/test_patch.py

@@ -28,15 +28,13 @@ from dulwich import porcelain
 from dulwich.repo import (
     Repo,
     )
-from dulwich.tests import (
-    TestCase,
-    )
 from dulwich.tests.compat.utils import (
+    CompatTestCase,
     run_git_or_fail,
     )
 
 
-class CompatPatchTestCase(TestCase):
+class CompatPatchTestCase(CompatTestCase):
 
     def setUp(self):
         super(CompatPatchTestCase, self).setUp()