Prefix capabilities with space, consistent with C Git.

dulwich/server.py

@@ -211,7 +211,7 @@ class Handler(object):
 
     @classmethod
     def capability_line(cls):
-        return b" ".join(cls.capabilities())
+        return b"".join([b" " + c for c in cls.capabilities()])
 
     @classmethod
     def capabilities(cls):

dulwich/tests/test_porcelain.py

@@ -644,7 +644,7 @@ class ReceivePackTests(PorcelainTestCase):
         exitcode = porcelain.receive_pack(self.repo.path, BytesIO(b"0000"), outf)
         outlines = outf.getvalue().splitlines()
         self.assertEqual([
-            b'00629e65bdcf4a22cdd4f3700604a275cd2aaf146b23 HEAD\x00report-status '
+            b'00639e65bdcf4a22cdd4f3700604a275cd2aaf146b23 HEAD\x00 report-status '
             b'delete-refs side-band-64k no-done',
             b'003f9e65bdcf4a22cdd4f3700604a275cd2aaf146b23 refs/heads/master',
             b'0000'], outlines)

dulwich/tests/test_server.py

@@ -127,7 +127,7 @@ class HandlerTestCase(TestCase):
             self.fail(e)
 
     def test_capability_line(self):
-        self.assertEqual(b'cap1 cap2 cap3', self._handler.capability_line())
+        self.assertEqual(b' cap1 cap2 cap3', self._handler.capability_line())
 
     def test_set_client_capabilities(self):
         set_caps = self._handler.set_client_capabilities