Re: [PATCH] pager: turn on "cat" optimization for DEFAULT_PAGER

[Junio C Hamano <gitster@pobox.com>]

Jeff King <peff@peff.net> writes:

> I'll venture my opinion. We should do this:
>
> -- >8 --
> Subject: pager: turn on "cat" optimization for DEFAULT_PAGER
>
> If the user specifies a pager of "cat" (or the empty
> string), whether it is in the environment or from config, we
> automagically optimize it out to mean "no pager" and avoid
> forking at all. We treat an empty pager variable similary.
>
> However, we did not apply this optimization when
> DEFAULT_PAGER was set to "cat" (or the empty string). There
> is no reason to treat DEFAULT_PAGER any differently. The
> optimization should not be user-visible (unless the user has
> a bizarre "cat" in their PATH). And even if it is, we are
> better off behaving consistently between the compile-time
> default and the environment and config settings.
>
> The stray "else" we are removing from this code was
> introduced by 402461a (pager: do not fork a pager if PAGER
> is set to empty., 2006-04-16). At that time, the line
> directly above used:
>
>    if (!pager)
> 	   pager = "less";
>
> as a fallback, meaning that it could not possibly trigger
> the optimization. Later, a3d023d (Provide a build time
> default-pager setting, 2009-10-30) turned that constant into
> a build-time setting which could be anything, but didn't
> loosen the "else" to let DEFAULT_PAGER use the optimization.
>
> Noticed-by: Dale R. Worley <worley@alum.mit.edu>
> Suggested-by: Matthieu Moy <Matthieu.Moy@grenoble-inp.fr>
> Signed-off-by: Jeff King <peff@peff.net>
> ---

Makes sense.  Thanks.

>  pager.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/pager.c b/pager.c
> index c1ecf65..fa19765 100644
> --- a/pager.c
> +++ b/pager.c
> @@ -54,7 +54,7 @@ const char *git_pager(int stdout_is_tty)
>  		pager = getenv("PAGER");
>  	if (!pager)
>  		pager = DEFAULT_PAGER;
> -	else if (!*pager || !strcmp(pager, "cat"))
> +	if (!*pager || !strcmp(pager, "cat"))
>  		pager = NULL;
>  
>  	return pager;