Re: [PATCH v2 0/7] making log --first-parent imply -m

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 2, 2020, 17:35 UTC
Message-ID: <xmqqsgd5rlwi.fsf@gitster.c.googlers.com>
In-Reply-To: <87mu3drynx.fsf@osv.gnss.ru>

Sergey Organov <sorganov@gmail.com> writes:

Show 6 quoted lines

> What I in fact have in mind is something like:
>
>   --diff-merges[=<parent-number>|c|cc|all]
>
> to have a single point of definition of the needed format of merges
> representation.

A command line option that takes _optional_ argument is evil; it hurts teachability (e.g. "why does this option always require "--opt=val" and refuses '--opt val'?"). Making the optional value configurable is even more so (e.g. "teacher said to use '--opt', but it does not behave the way she taught---ah, I have this config").

> Then comes the question of the default. "all" is what'd make it behave
> as "-m" behaves now. If it's too late for --diff-merges to have
> different default, could the default possibly be a configuration
> option rather than yet another command-line option?

Introduce --diff-parent=(none|<parent-number>|c|cc|all) that is different from --diff-merges, and -m and --[no-]diff-merges can be defined in terms of that, at which point we can gradually deprecate them if we wanted to, no?