git-cl: Print Rietveld deprecation warning

To encourage folks to upload to Gerrit.

Bug: 685321
Change-Id: I849ed53f95a2205959237fe825ffe41e349ff8c7
Reviewed-on: https://chromium-review.googlesource.com/510963Reviewed-by: Andrew Bonventre <andybons@chromium.org>
Commit-Queue: Aaron Gable <agable@chromium.org>

git_cl.py

@@ -1592,6 +1592,16 @@ class Changelist(object):
       base_branch = self.GetCommonAncestorWithUpstream()
       git_diff_args = [base_branch, 'HEAD']
 
+    # Warn about Rietveld deprecation for initial uploads to Rietveld.
+    if not self.IsGerrit() and not self.GetIssue():
+      print('=====================================')
+      print('NOTICE: Rietveld is being deprecated. '
+            'You can upload changes to Gerrit with')
+      print('  git cl upload --gerrit')
+      print('or set Gerrit to be your default code review tool with')
+      print('  git config gerrit.host true')
+      print('=====================================')
+
     # Fast best-effort checks to abort before running potentially
     # expensive hooks if uploading is likely to fail anyway. Passing these
     # checks does not guarantee that uploading will not fail.

tests/git_cl_test.py

@@ -982,7 +982,15 @@ class TestGitCl(TestCase):
     self.mock(sys, 'stdout', stdout)
     with self.assertRaises(SystemExitMock):
       git_cl.main(['upload', '--send-mail'])
-    self.assertEqual('', stdout.getvalue())
+    self.assertEqual(
+        '=====================================\n'
+        'NOTICE: Rietveld is being deprecated. '
+        'You can upload changes to Gerrit with\n'
+        '  git cl upload --gerrit\n'
+        'or set Gerrit to be your default code review tool with\n'
+        '  git config gerrit.host true\n'
+        '=====================================\n',
+        stdout.getvalue())
 
   def test_bug_on_cmd(self):
     self._run_reviewer_test(