cli: Allow to run --preapre-only w/o additional information

/reviewed-on !4

kedifa/cli.py

@@ -146,21 +146,20 @@ def updater(*args):
     'state',
     type=str,
     help='Path to JSON state file for fallback recognition, on which locks '
-         'will happen.'
+         'will happen.',
+    nargs='?'
   )
 
   parser.add_argument(
     '--identity',
     type=argparse.FileType('r'),
     help='Certificate to identify itself on the URL.',
-    required=True
   )
 
   parser.add_argument(
     '--server-ca-certificate',
     type=argparse.FileType('r'),
     help='CA Certificate of the server.',
-    required=True
   )
 
   parser.add_argument(
@@ -200,10 +199,12 @@ def updater(*args):
 
   u = Updater(
     parsed.sleep, parsed.mapping.name, parsed.state, parsed.master_certificate,
-    parsed.on_update, parsed.identity.name, parsed.server_ca_certificate.name,
+    parsed.on_update,
+    parsed.identity and parsed.identity.name or None,
+    parsed.server_ca_certificate and parsed.server_ca_certificate.name or None,
     parsed.once, parsed.prepare_only
   )
   parsed.mapping.close()
-  parsed.identity.close()
-  parsed.server_ca_certificate.close()
+  parsed.identity and parsed.identity.close()
+  parsed.server_ca_certificate and parsed.server_ca_certificate.close()
   u.loop()

kedifa/test.py

@@ -1339,6 +1339,16 @@ class KedifaUpdaterUpdateCertificateTest(
     self.assertTrue(update)
     self.assertState({self.certificate_file_name: True})
 
+
+class KedifaUpdaterUpdateCertificatePrepareTest(
+  KedifaUpdaterMixin, unittest.TestCase):
+  def setUp(self):
+    super(KedifaUpdaterUpdateCertificatePrepareTest, self).setUp()
+    certificate_file = tempfile.NamedTemporaryFile(
+      dir=self.testdir, delete=True)
+    certificate_file.close()
+    self.certificate_file_name = certificate_file.name
+
   def _prepare(self, certificate, master_content, fallback=None):
     if certificate:
       with open(self.certificate_file_name, 'w') as fh:
@@ -1362,7 +1372,7 @@ class KedifaUpdaterUpdateCertificateTest(
       mapping = '%s %s' % (mapping, fallback_file.name)
     self.setupMapping(mapping)
     u = updater.Updater(
-      1, self.mapping, self.state, master_file, None, None,
+      1, self.mapping, None, master_file, None, None,
       None, True, True)
     with mock.patch.object(
       updater.Updater, 'fetchCertificate') as fetchCertificate: