correctly prepended.

gives access to the generated command, instead of it being run

Previously only the long versions of options were correctly flagged
as booleans, but the -b and -B options do not have long alternatives
so they need to be supported too. And for familiarity to command line
users we should support other single-char switches too

specified as pathlib.Path objects, so they can be differentiated from input
values.

items (where possible). Result standard output renamed from "output" to
"stdout".

is used in conjunction with submit=True