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

From: Alex Henrie <alexhenrie24@gmail.com>
Date: Jul 12, 2021, 16:29 UTC
Message-ID: <CAMMLpeQYwPDjc8WVFmwVismJPBYAifQS96+R8hDj+pch_db+Qg@mail.gmail.com>
In-Reply-To: <00e246b1-c712-e6a5-5c27-89127d796098@gmail.com>

On Mon, Jul 12, 2021 at 4:21 AM Phillip Wood <phillip.wood123@gmail.com> wrote:

Show 32 quoted lines

>
> 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?

-Alex