-Zhelp still requires input file

[timvisee]

tectonic -h suggests to use tectonic -Zhelp to view unstable options.

This command doesn't work though, as an <input> file is required.

$ tectonic -Zhelp
error: The following required arguments were not provided:
    <input>

USAGE:
    tectonic <input> --outfmt <format> --chatter <level> -Z <option>... --pass <pass> --format <path> --color <when>

For more information try --help

$ tectonic -Zhelp -
Available unstable options:

    -Z help                     Lists all unstable options
    -Z continue-on-errors       Keep compiling even when severe errors occur
    -Z min-crossrefs=<num>      Equivalent to bibtex's -min-crossrefs flag - "include after <num>
                                    crossrefs" [default: 2]
    -Z paper-size=<spec>        Change the default paper size [default: letter]
    -Z search-path=<path>       Also look in <path> for files, like TEXINPUTS. Can be specified
                                    multiple times.
    -Z shell-escape             Enable \write18