Re: [PATCH v2 04/14] pull: cleanup autostash check

From: Elijah Newren <newren@gmail.com>
To: Felipe Contreras <felipe.contreras@gmail.com>
Cc: "Git Mailing List" <git@vger.kernel.org>,
	"Vít Ondruch" <vondruch@redhat.com>,
	"Alex Henrie" <alexhenrie24@gmail.com>,
	"Junio C Hamano" <gitster@pobox.com>, "Jeff King" <peff@peff.net>,
	"Philip Oakley" <philipoakley@iee.email>,
	"Theodore Y . Ts'o" <tytso@mit.edu>,
	"Jacob Keller" <jacob.keller@gmail.com>,
	"John Keeping" <john@keeping.me.uk>,
	"Richard Hansen" <rhansen@rhansen.org>,
	"Brian M. Carlson" <sandals@crustytoothpaste.net>,
	"W. Trevor King" <wking@tremily.us>
Subject: Re: [PATCH v2 04/14] pull: cleanup autostash check
Date: Fri, 4 Dec 2020 16:57:59 -0800	[thread overview]
Message-ID: <CABPp-BEsQWsHMAmwc3gmJnXcS+aR-FtoMJxBRQ=BpARP49-L-Q@mail.gmail.com> (raw)
In-Reply-To: <CAMP44s0D42s=q8TJqxwswOHb4PO-NW6SEUt-LwfvqiGgvkre9A@mail.gmail.com>

On Fri, Dec 4, 2020 at 4:47 PM Felipe Contreras
<felipe.contreras@gmail.com> wrote:
>
> On Fri, Dec 4, 2020 at 5:07 PM Elijah Newren <newren@gmail.com> wrote:
> >
> > On Thu, Dec 3, 2020 at 10:16 PM Felipe Contreras
> > <felipe.contreras@gmail.com> wrote:
> > >
> > > This essentially reverts commit f15e7cf5cc.
> > >
> > > Once commit d9f15d37f1 introduced the autostash option for the merge
> > > mode, it's not necessary to skip the fast-forward run_merge() when
> > > autostash is set.
> >
> > It helps reviewers and future code readers if you provide a little
> > context when referring to commits, making use of git log's
> > --pretty=reference option to get the output.
>
> Yes, I actually have this alias:
>
>   short = show --quiet --format='%C(auto)%h (%s)%C(reset)'
>
> Which shows almost the same thing. I've updated it to
> --format=reference. Thanks for the suggestion.
>
> And I usually add those descriptions.
>
> > So, for example, here
> > your commit would read:
> >
> > """
> > This essentially reverts commit f15e7cf5cc (pull: ff --rebase
> > --autostash works in dirty repo, 2017-06-01).
> >
> > Once commit d9f15d37f1 (pull: pass --autostash to merge, 2020-04-07)
> > introduced the autostash option for the merge
> > mode, it's not necessary to skip the fast-forward run_merge() when
> > autostash is set.
> > """
> >
> > I still found it slightly hard to follow the explanation even with the
> > added summaries, though.
>
> And that's the reason I didn't add them. You need to look at both the
> commits to understand why one cancels the other. In my opinion in this
> particular case the description only makes the text harder to read.
>
> Probably some better $subjects like f15e7cf5cc (pull: skip ff merge
> shortcut on --rebase --autostash) would have helped.
>
> > An extra sentence at the end of the second
> > paragraph to make it clear what is being changed ("So, change the code
> > to fast-forward even when autostash is set.") seems to help.
>
> OK. That's implied by "it's not necessary to skip the fast-forward"
> but it's better to be explicit.
>
> How about this:
>
> Currently "git pull --rebase" takes a shortcut in the case a
> fast-forward merge is possible; run_merge() is called with --ff-only.
>
> However, "git merge" didn't have an --autostash option, so, when "git
> pull --rebase --autostash" was called *and* the fast-forward merge
> shortcut was taken, then the pull failed.
>
> This was fixed in commit f15e7cf5cc (pull: ff --rebase --autostash
> works in dirty repo, 2017-06-01) by simply skipping the fast-forward
> merge shortcut.
>
> Later on "git merge" learned the --autostash option [a03b55530a
> (merge: teach --autostash option, 2020-04-07)], and so did "git pull"
> [d9f15d37f1 (pull: pass --autostash to merge, 2020-04-07)].
>
> Therefore it's not necessary to skip the fast-forward merge shortcut
> anymore when called with --rebase --autostash.
>
> Let's always take the fast-forward merge shortcut by essentially
> reverting f15e7cf5cc.

Yes, very nice!  Thanks.

Elijah