improve error message on bad cli argument (#371)

currently the error messages have the shortopt hardcoded in them, even
when the user actually entered a longopt:

	$ ./nsxiv --framerate v
	nsxiv: Invalid argument for option -A: v

and as far as I see, there's no way to *reliably* tell weather we're
processing a longopt or a shortopt. perhaps we can do some shenanigangs
with `optind` but that seems finicky at best.

and it seems like other coreutils which support longopt has similar issues:

	$ xargs --max-procs=z
	xargs: invalid number "z" for -P option

utils like `grep` and `head` seems to work-around it by not mentioning the flag:

	$ head --lines=z
	head: invalid number of lines: ‘z’
	$ grep --max-count=l
	grep: invalid max count

this patch does the same thing as `grep/head` and omits the flag from
the error message.

Closes: https://codeberg.org/nsxiv/nsxiv/issues/368

Reviewed-on: https://codeberg.org/nsxiv/nsxiv/pulls/371
Reviewed-by: Berke Kocaoğlu <berke.kocaoglu@metu.edu.tr>

0 files changed, 0 insertions, 0 deletions