Set ignoreSubmodule=all for all repos.

Bug: 1415507

Change-Id: I840508c6972e4640793a12aba287ed8dedfe64c5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4641611
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
Commit-Queue: Joanna Wang <jojwang@chromium.org>
diff --git a/tests/gclient_scm_test.py b/tests/gclient_scm_test.py
index 8c85520..06220ed 100755
--- a/tests/gclient_scm_test.py
+++ b/tests/gclient_scm_test.py
@@ -393,6 +393,8 @@
     self.assertEqual(file_list, expected_file_list)
     self.assertEqual(scm.revinfo(options, (), None),
                       'a7142dc9f0009350b96a11f372b6ea658592aa95')
+    self.assertEqual(scm._Capture(['config', '--get', 'diff.ignoreSubmodules']),
+                     'all')
     sys.stdout.close()
 
   def testUpdateMerge(self):