the short opt -t does not accept optional argument since it'd
break short option chaining.
e.g `nsxiv -tp` currently works as `nsxiv -t -p` but if `-t`
accepted optional argument then it'd stop working since "p" will
be interpreted as argument to `-t` instead of being a flag.
ref: https://codeberg.org/nsxiv/nsxiv/issues/404
11558c9fcf