codereview: add golang-dev@googlegroups.com     automatically in "hg mail". also, avoid "empty list means all modified files in client" bug
codereview: add golang-dev@googlegroups.com
    automatically in "hg mail".
also, avoid "empty list means all modified files in client" bug

R=gri, cw
CC=golang-dev
http://codereview.appspot.com/174072

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