Counting lines correctly in psql help displays

I wrote:
> BTW, I noticed that the PageOutput line counts for psql's usage(),
> slashUsage(), and helpVariables() were all three wrong, which I'm afraid
> has been their usual state in the past too. Since commit 07c8651dd91d5aea
> there's been a pretty easy way to check them, which I added comments
> about; but I don't hold much hope that that will fix anything. I wonder
> whether there's some way to not need to maintain those counts manually.

I seem to recall past proposals to fix that by putting the lines into
static char * arrays, which foundered on the fact that the output's not
necessarily constant. But it suddenly strikes me that there's an easy
fix. We can generate the output into a PQExpBuffer, which is just as
flexible as fprintf() is today, then count the lines and finally print.

Ordinarily I might think that was overkill, but given the number of times
that we've failed to update those counts in the past, I think this is
definitely a worthwhile investment in maintainability.

Or we could just give up and replace the counts by INT_MAX, forcing use
of the pager unless you've turned it off. All of those outputs are long
enough now that it's hard to believe there are any common screen layouts
where you don't end up invoking the pager anyway. (usage() is 60 lines,
the others are more.) This is probably the reason why we've seldom
noticed they're wrong --- it barely matters anymore.

One way or the other I think it's past time to get out of the business
of maintaining these counts. I'm willing to do the work of using a
PQExpBuffer if people think it's worth the trouble to have an accurate
count, but it may not be worth the code space.

Thoughts?

regards, tom lane