function git_ahead -a ahead behind diverged none
    command git rev-list --count --left-right "@{upstream}...HEAD" ^ /dev/null | awk "

        /0\t0/          { print \"$none\"       ? \"$none\"     : \"+\";    exit 0 }
        /[0-9]+\t0/     { print \"$behind\"     ? \"$behind\"   : \"-\";    exit 0 }
        /0\t[0-9]+/     { print \"$ahead\"      ? \"$ahead\"    : \"+\";    exit 0 }
        //              { print \"$diverged\"   ? \"$diverged\" : \"±\";    exit 0 }
    "
end