cmd/coordinator: don't push Gerrit-internal refs to github

Change-Id: Ie7b0d97e6450be2e31a61bd2f3556060c07d7255
Reviewed-on: https://go-review.googlesource.com/32315
Reviewed-by: Russ Cox <rsc@golang.org>

cmd/coordinator/watcher_process.go

@@ -959,6 +959,11 @@ func (r *Repo) push() (err error) {
 
 		var pushRefs []string
 		for ref, hash := range local {
+			if strings.Contains(ref, "refs/users/") ||
+				strings.Contains(ref, "refs/cache-auto") ||
+				strings.Contains(ref, "refs/changes/") {
+				continue
+			}
 			if remote[ref] != hash {
 				pushRefs = append(pushRefs, ref)
 			}