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From: Elijah Newren <newren@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: Tao Klerks via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org, Tao Klerks <tao@klerks.biz>
Subject: Re: [PATCH] RFC: switch: allow same-commit switch during merge if conflicts resolved
Date: Tue, 2 May 2023 17:34:00 -0700	[thread overview]
Message-ID: <CABPp-BEd_53EfEfFfWf8zEt0K7Mp4iMzN=q6smK4_08xfj6Tiw@mail.gmail.com> (raw)
In-Reply-To: <xmqq1qjy1xv2.fsf@gitster.g>

On Tue, May 2, 2023 at 9:50 AM Junio C Hamano <gitster@pobox.com> wrote:
>
> Elijah Newren <newren@gmail.com> writes:
>
> > By the way, it was a problem that git-checkout wasn't updated to have
> > the same safety that git-switch has.  We should fix that.  (It's on my
> > todo list, along with adding other
> > prevent-erroneous-command-while-in-middle-of-other-operation cases.)
>
> Yes.
>
> > I'm worried this is likely to lead us into confusing UI mismatches,
> > and makes it harder to understand the appropriate rules of what can
> > and cannot be done.  A very simple "no switching branches in the
> > middle of operations" is a very simple rule, and saves users from lots
> > of headaches.
> >
> > Granted, expert users may understand that with the commit being the
> > same, there is no issue.  But expert users can use `git update-ref` to
> > tweak HEAD, or edit .git/HEAD directly, and accept the consequences.
> > Why do we need to confuse the UI for the sake of expert users who
> > already have an escape hatch?
> >
> > More importantly, though...
> >
> >> Change the behavior of "git switch" and "git checkout" to no longer delete
> >> merge metadata, nor prohibit the switch, if a merge is in progress and the
> >> commit being switched to is the same commit the HEAD was previously set to.
> >
> > Even if there are conflicts?  For rebases, cherry-picks, ams, and
> > reverts too?  (Does allowing this during rebases and whatnot mean that
> > --abort becomes really funny?  Does it mean that some commits are
> > applied to one branch, and all commits are applied to another?  What
> > about autostashes?  Does it interact weirdly with --update-refs?
> > etc.)
> >
> > I think this change is premature unless it discusses all these cases,
>
> It is pretty much what I wanted to say about why we haven't done
> this in <https://lore.kernel.org/git/xmqqpm7k6ojz.fsf@gitster.g/>,
> so it makes two of us ;-).  I didn't look at Tao's RFC patch but if
> the way it determines "we are in a middle of conflicted merge and
> we'll allow switching to the same commit only in this case" were
> "the index has an unmerged entry", then it is an overly broad test
> and the consequences of allowing the switch for these other merge-y
> operations that are ongoing must be evaluated.

He does tie it specifically to "is-this-a-merge-operation" (and
actually doesn't check for conflicts at all since there are existing
checks he leaves untouched).  That certainly prevents some problems,
but doesn't address my concerns.

I think the usecase Tao presents has multiple simple workarounds, and
I'm worried that the particular proposal might paint us into a corner.

Personally, I think that before we consider a
merge-specific-if-no-conflicts exception, someone should evaluate all
the cases where exceptions could or should be allowed, get a
documented story about them, and then if a consistent-ish UI is
possible then propose patches to start taking us down this path.

  reply	other threads:[~2023-05-03  0:35 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-02  6:27 [PATCH] RFC: switch: allow same-commit switch during merge if conflicts resolved Tao Klerks via GitGitGadget
2023-05-02 15:55 ` Elijah Newren
2023-05-02 16:50   ` Junio C Hamano
2023-05-03  0:34     ` Elijah Newren [this message]
2023-05-04  5:01   ` Tao Klerks
2023-05-05  5:06     ` Tao Klerks
2023-05-07  2:57       ` Elijah Newren
2023-05-07  2:48     ` Elijah Newren
2023-05-07 22:01       ` Felipe Contreras
2023-05-08  8:30         ` Tao Klerks
2023-05-08 16:13           ` Felipe Contreras
2023-05-08 16:58             ` Tao Klerks
2023-05-08 19:18               ` Junio C Hamano
2023-05-09  1:55               ` Felipe Contreras
2023-05-08 10:44       ` Tao Klerks
2023-05-11  7:06         ` Elijah Newren
2023-05-21 20:08         ` Tao Klerks

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