Re: Better error message when --single is not the first arg to postgres executable

If I am reading your patch correctly, we have lost the behavior of least
surprise in which the first "meta" argument overrides all others:

$ bin/postgres --version --boot --extrastuff
postgres (PostgreSQL) 16.2

What about just inlining --version and --help e.g.

else if (strcmp(argv[i], "--version") == 0 || strcmp(argv[i], "-V") == 0)
{
     fputs(PG_BACKEND_VERSIONSTR, stdout);
     exit(0);
}

I'm fine with being more persnickety about the other options; they are much
rarer and not unixy.

However, there's a complication:
> ...
> This remaining discrepancy might be okay, but I was really hoping to reduce
> the burden on users to figure out the correct ordering of options.  The
> situations in which I've had to use single-user mode are precisely the
> situations in which I'd rather not have to spend time learning these kinds
> of details.
>

Yes, that's unfortunate. But I'd be okay with the db-last requirement as
long as the error message is sane and points one in the right direction.

Cheers,
Greg