A push naming one machine reached the verb without it and pushed every
machine behind (hq issue 244). The controller now refuses any argument a
verb does not declare, any it composed its command line without, and a
switch that is not true or false; a push that names no machine says first
that it is the whole mesh. Tests walk every served verb: no argument is
ever ignored, and every flag of a verb's command, read from the source, is
in its schema or accounted for. plan gains files, push behind, builds and
plans limit.