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

[Felipe Contreras <felipe.contreras@gmail.com>]

Alex Henrie wrote:
> On Sun, Jul 11, 2021 at 11:08 AM Felipe Contreras
> <felipe.contreras@gmail.com> wrote:
> >
> > 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.
> >
> > I don't know where that is being said, but it's wrong: --ff-only is
> > meant for merge only.
> >
> > > --- a/builtin/pull.c
> > > +++ b/builtin/pull.c
> > > @@ -1046,9 +1046,14 @@ int cmd_pull(int argc, const char **argv, const char *prefix)
> > >
> > >       can_ff = get_can_ff(&orig_head, &merge_heads.oid[0]);
> > >
> > > -     if (rebase_unspecified && !opt_ff && !can_ff) {
> > > -             if (opt_verbosity >= 0)
> > > -                     show_advice_pull_non_ff();
> > > +     if (!can_ff) {
> > > +             if (opt_ff) {
> > > +                     if (!strcmp(opt_ff, "--ff-only"))
> > > +                             die_ff_impossible();
> >
> > As I've mentioned multiple times already, this is wrong.
> >
> > The advice clearly says:
> >
> >   You can also pass --rebase, --no-rebase, or --ff-only on the command
> >   line to override the configured default per invocation.
> >
> > With your patch now this is even less true:
> >
> >   git -c pull.ff=only pull --rebase
> 
> I think it's an improvement over the current situation. --no-rebase
> does not override pull.ff=only, so it makes sense that --rebase does
> not override pull.ff=only either.

I disagree, but that's not the point, the point is that now the advice
message is wrong since --rebase doesn't override pull.ff=only.

Additionally the documentation is inaccurate too because at no point
does pull.ff mention anything about rebase:

pull.ff::
	By default, Git does not create an extra merge commit when merging
	a commit that is a descendant of the current commit. Instead, the
	tip of the current branch is fast-forwarded. When set to `false`,
	this variable tells Git to create an extra merge commit in such
	a case (equivalent to giving the `--no-ff` option from the command
	line). When set to `only`, only such fast-forward merges are
	allowed (equivalent to giving the `--ff-only` option from the
	command line). This setting overrides `merge.ff` when pulling.

-- 
Felipe Contreras