Add a setting to squash Gerrit uploads by default, and a --no-squash command line option to overrid…

tests/git_cl_test.py

Index: tests/git_cl_test.py
diff --git a/tests/git_cl_test.py b/tests/git_cl_test.py
index 220e59164385ab2d8774de787cae2cc9450c9e19..b5e14dcc8fb6de11f43bae759fbcd3ec77a2e88a 100755
--- a/tests/git_cl_test.py
+++ b/tests/git_cl_test.py
@@ -585,6 +585,7 @@ class TestGitCl(TestCase):
   def _gerrit_upload_calls(description, reviewers, squash,
                            expected_upstream_ref='origin/refs/heads/master'):
     calls = [
+        ((['git', 'config', '--bool', 'gerrit.squash-uploads'],), 'false'),
         ((['git', 'log', '--pretty=format:%s\n\n%b',
            'fake_ancestor_sha..HEAD'],),
          description)