Add more test coverage to push-to-trunk script.

Ensure that fetching commits works with huge change logs. The verbosity option will help debugging when dcommit hangs.

BUG=
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/70143003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17645 ce2b1a6d-e550-0410-aec6-3dcde31c8c00