Re: [PATCH 00/26] git-log: implement new --diff-merge options

From: Elijah Newren <newren@gmail.com>
Date: Dec 8, 2020, 20:52 UTC
Message-ID: <CABPp-BGuLX8Msghbo6L7vB2Wqys=Xg_uvV2Aui-1q4-+ijuNEw@mail.gmail.com>
In-Reply-To: <87y2i8dptj.fsf@osv.gnss.ru>

Hi Sergey,

On Tue, Dec 8, 2020 at 12:07 PM Sergey Organov <sorganov@gmail.com> wrote:

Show 21 quoted lines

>
> Sergey Organov <sorganov@gmail.com> writes:
>
>
> [...]
>
> > The series also cleanup logic of handling of diff merges options and
> > fix an issue found in the original implementation where logically
> > mutually exclusive options -m/-c/--cc failed to actually override each
> > other.
>
> Working further on this, I've noticed very irregular interactions
> between -m/-c/--cc and --oneline:
>
> 1. --oneline disables -m output for 'git log', and leaves -m output enabled
> for 'git show':
>
> $ /usr/bin/git show -n1 -m --oneline 2e673356aef | wc -l
> 80
> $ /usr/bin/git log -n1 -m --oneline 2e673356aef | wc -l
> 1

If you leave off --oneline, you'll note that git show produces a diff and git log does not (regardless of whether 2e673356aef is a merge commit or a regular commit). So, I don't think this is related to --oneline.

Show 12 quoted lines

> 2. For 'git log', --oneline disables -m output, and leaves -c/--cc output
> enabled:
>
> $ /usr/bin/git log -n1 -m --oneline 2e673356aef | wc -l
> 1
> $ /usr/bin/git log -n1 -c --oneline 2e673356aef | wc -l
> 16
> $ /usr/bin/git log -n1 --cc --oneline 2e673356aef | wc -l
> 16
>
> The question is: what's the right interaction between --oneline and
> -m/-c/--cc?

I believe the right question is: Should -m be a no-op unless -p is also specified? In the past, --cc and -c were no-ops except when -p was also specified. It was somewhat unfriendly and surprising, and thus was changed so that --cc and -c implied -p (and thus would cause output for non-merge commits to be shown differently, namely shown with a diff, in addition to affecting the type of diff shown for merge commits). I think -m was overlooked at the time.

> I tend to think they should be independent, so that --oneline doesn't
> affect diff output, and then the only offender is -m.

I agree that they should be independent, but I believe they are already independent unless you have more evidence of weirdness somewhere. The differences you are seeing are due to -m, -c, and --cc being handled differently, and I think we should probably just give -m the same treatment that we give to -c and --cc (namely, make all three imply -p).

Hope that helps, Elijah