Determine actually given command line arguments

[Jussi Piitulainen]

Henry Leyh writes:

> But now I would also like to be able to _write_ such a config file
> FILE that can be read in a later run.  And FILE should contain only
> those arguments that were given on the command line.
> 
> Say, I tell argparse to look for arguments -s|--sopt STRING,
> -i|--iopt INT, -b|--bopt [BOOL], -C CONFFILE.  Then 'prog -s bla -i
> 42 -C cfile' should produce a confparser compatible cfile which
> contains
> 
>    [my_options]
>    sopt = blah
>    iopt = 42
> 
> and not 'bopt = False' (if False was the program's default for
> bopt).

Could you instead write those options that differ from the defaults?
You could parse an actual command line and an empty command line, and
work out the difference.

So 'prog -i 3' would not cause 'iopt = 3' to be written if 3 is the
default for iopt, but would that be a problem?