The mirror of jschoubben/car-hunter on ace said only "git -C: error:": git writes a bare
"error:" before the forge's message, and the reason kept the first non-empty line. forgekey.Said
keeps every line that says something, leaves bare prefixes out, joins them and bounds them at
600 bytes; every git and ssh-keygen reason of buildstep and forgekey goes through it, and the
mirror's commands are named by their verb, not by -C.