The most important git subcommand in depot_tools never had a man
page until today. And now "git help cl" and "git cl --help" will
work.

BUG=695623

Change-Id: Ic0d05fa8d70d2ef6e71d58e0d7d3e7adc4a2fa32
Reviewed-on: https://chromium-review.googlesource.com/447216Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Aaron Gable <agable@chromium.org>