Subject: Re: [PATCH] mergetools/meld: do not rely on the output of `meld --help`

From: Junio C Hamano <[email-masked]>
Date: Wed, 15 Oct 2014 12:04:27 -0700

David Aguilar <[email-masked]> writes:

> We cannot rely on the output of `meld --help` when determining
> whether or not meld understands the --output option.
>
> Newer versions of meld print a generic help message that does not
> mention --output even though it is supported.

This obviously breaks those who have happily been using their
installed version of meld that understands and shows --output in the
help text.  Is that a minority that is rapidly diminishing?

I would understand it if the change were

 - a configuration tells us to use or not use --output; when it is
   set, then we do not try auto-detect by reading --help output

 - when that new configuration is not set, we keep the current code
   to read --help output, which may fail for recent meld but that is
   not a regression.

When versions of meld that support --output but do not mention it in
their --help text are overwhelming majority, we would want to flip
the fallback codepath from "read --help and decide" to "assume that
--output can be used", but I do not know if now is the time to do
so.