git-number cannot commit-tree without user config
git-number cannot commit-tree without user config

user.name and/or user.email may be not configured, so specify them
explictly for commit-tree.

R=iannucci@chromium.org
BUG=354276

Review URL: https://codereview.chromium.org/222103006

git-svn-id: bd64dd6fa6f3f0ed0c0666d1018379882b742947@261256 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

svn2github/chromium-depot-tools,svn2github/chromium-depot-tools,svn2github/chromium-depot-tools