x/tools/dashboard/watcher: convert to git
x/tools/dashboard/watcher: convert to git

LGTM=dsymonds
R=bradfitz, dsymonds
CC=golang-codereviews
https://golang.org/cl/177660043

proppy/build,golang/build,golang/build,proppy/build,evandbrown/build,golang/build,proppy/build,proppy/build,evandbrown/build,golang/build,evandbrown/build