This makes it easier to type without using the shift-key, so an user can type
'git cl set-commit' and it'll find CMDset_commit.

R=xusydoc@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/22918019

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@219054 0039d316-1c4b-4281-b951-d872f2087c98