Add option for git-repo to support 'silent' uploads

When --ne/--no-emails is added to 'repo upload' command line, gerrit
server will not generate notification emails.

project.py:Project.UploadForReview method is modified to accept a
string recognizable by gerrit to indicate different sets of destination
email addressees, but the upload command line allows only one option -
disable sending emails completely.

Default repo upload behavior is not being changed.

TEST=tried in the Chrome OS repo, observed that patches uploaded with
     --ne or --no-emails indeed do not trigger any emails, while
     patches uploaded without these command line options still trigger
     email notifications.

Change-Id: I0301edec984907aedac277d883bd0e6d3099aedc

0 files changed, 0 insertions, 0 deletions