Re: why does git set X in LESS env var?

From: Jeff King <peff@peff.net>
Date: Oct 12, 2023, 00:04 UTC
Message-ID: <20231012000416.GA520855@coredump.intra.peff.net>
In-Reply-To: <xmqqa5sokdd3.fsf@gitster.g>

On Wed, Oct 11, 2023 at 03:23:20PM -0700, Junio C Hamano wrote:

Show 18 quoted lines

> Christoph Anton Mitterer <calestyo@scientia.org> writes:
> 
> > But I still don't get from that why X would be needed?
> >
> > My less manpage documents it as:
> >> -X or --no‐init
> >>     Disables sending the termcap initialization and deinitialization
> >>     strings to the terminal.  This is sometimes desirable if the
> >>     deinitialization string does something unnecessary, like clearing
> >>     the screen.
> >
> > Is it to avoid clearing the screen?
> 
> I think that was the reason we added it back in 2005.  In any case,
> asking "why" is not a useful use of anybody's time, because it is
> very unlikely to change in the official version we ship, and because
> it is so easy for any individual who does not like it to drop by
> exporting the $LESS environment variable.

I agree it is probably not worth changing now, but I think the history here is a little interesting.

Yes, I think "X" was added because less would clear the screen after exiting, and with "F" this meant you'd see nothing. Here's a thread from the same time period discussing it:

  https://lore.kernel.org/git/cc723f590610210623sbee2075i5f2fd441cceb84ae@mail.gmail.com/

But I also think this was a pretty well-known annoyance with "less" back then.

However, I can't seem to reproduce it now! Digging into the history and the changelog, this note is in "changes between less versions 487 and 530":

  Don't output terminal init sequence if using -F and file fits on one
  screen.

So it seems like the problem has been fixed inside less for recent versions. And in theory we _could_ drop "-X" if it is causing problems. That version of less is ~5 years old. It does seem a little premature to assume everybody has it. And as you say, if there are people who really care about their LESS options, it is easy for them to override it.

-Peff