Warn before uploading more than one commit to Gerrit.

BUG=none

Review URL: https://codereview.chromium.org/259523006

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@267480 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/tests/git_cl_test.py b/tests/git_cl_test.py
index 9234fb2..2d20440 100755
--- a/tests/git_cl_test.py
+++ b/tests/git_cl_test.py
@@ -588,6 +588,7 @@
            description)
           ]
     calls += [
+        ((['git', 'rev-list', 'origin/master...'],), ''),
         ((['git', 'config', 'rietveld.cc'],), '')
         ]
     receive_pack = '--receive-pack=git receive-pack '