chg: be stricter about checking invocation of `serve` command Few tests run serve command in form of `hg -R <repo> serve` which leads to chg thinking that it's not a serve command and failing tests. We become more stricter in checking for the serve command. This fixes test-server-view.t, test-remote-hidden.t, test-remotefilelog-http.t, test-phases-exchange.t, test-wireproto-content-redirects.t with chg.