Re: [PATCH] pull: abort if --ff-only is given and fast-forwarding is impossible

From: Felipe Contreras <felipe.contreras@gmail.com>
To: Alex Henrie <alexhenrie24@gmail.com>,
	Phillip Wood <phillip.wood123@gmail.com>
Cc: "Git mailing list" <git@vger.kernel.org>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Junio C Hamano" <gitster@pobox.com>,
	"Felipe Contreras" <felipe.contreras@gmail.com>,
	"Elijah Newren" <newren@gmail.com>
Subject: Re: [PATCH] pull: abort if --ff-only is given and fast-forwarding is impossible
Date: Mon, 12 Jul 2021 12:43:03 -0500	[thread overview]
Message-ID: <60ec7f276909f_a4525208c7@natae.notmuch> (raw)
In-Reply-To: <CAMMLpeQYwPDjc8WVFmwVismJPBYAifQS96+R8hDj+pch_db+Qg@mail.gmail.com>

Alex Henrie wrote:
> On Mon, Jul 12, 2021 at 4:21 AM Phillip Wood <phillip.wood123@gmail.com> wrote:
> >
> > On 11/07/2021 02:26, Alex Henrie wrote:
> > > The warning about pulling without specifying how to reconcile divergent
> > > branches says that after setting pull.rebase to true, --ff-only can
> > > still be passed on the command line to require a fast-forward. Make that
> > > actually work.
> >
> > Thanks for revising this patch, I like this approach much better. I do
> > however have some concerns about the interaction of pull.ff with the
> > rebase config and command line options. I'd naively expect the following
> > behavior (where rebase can fast-forward if possible)
> >
> >    pull.ff  pull.rebase  commandline  action
> >     only     not false                rebase
> >     only     not false   --no-rebase  fast-forward only
> >      *       not false    --ff-only   fast-forward only
> >     only     not false    --ff        merge --ff
> >     only     not false    --no-ff     merge --no-ff
> >     only       false                  fast-forward only
> >     only       false      --rebase    rebase
> >     only       false      --ff        merge --ff
> >     only       false      --no-ff     merge --no-ff
> >
> > I don't think enforcing fast-forward only for rebases makes sense unless
> > it is given on the command line. If the user gives `--rebase`
> > `--ff-only` on the command line then we should either error out or take
> > the last one in which case `pull --rebase --ff-only` would fast-forward
> > only but `pull --ff-only --rebase` would rebase. We should also decide
> > what to do when the user has pull.ff set to something other than only
> > and also has pull.rebase to something other than false set - I'd guess
> > we'd want to rebase unless there is a merge option on the command line
> > but I haven't thought about those cases.
> 
> I was thinking of --rebase and --ff-only as orthogonal variables.
> Nevertheless, we could make --rebase imply --ff, which would be pretty
> easy to explain in the documentation for the command-line options.
> That way, even though pull.rebase=true with pull.ff=only would enforce
> fast-forward-only, the user could easily override it with `git pull
> -r`. Would you accept that compromise?

What happens if the user has configured `pull.ff=no`?

-- 
Felipe Contreras