Add a setting to squash Gerrit uploads by default, and a --no-squash command line option to override it.

BUG=nope

Review URL: https://codereview.chromium.org/1584703005

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@298260 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/tests/git_cl_test.py b/tests/git_cl_test.py
index 220e591..b5e14dc 100755
--- a/tests/git_cl_test.py
+++ b/tests/git_cl_test.py
@@ -585,6 +585,7 @@
   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)