Re: Pick the right default and stop warn on `git pull`

From: Felipe Contreras <felipe.contreras@gmail.com>
Date: Nov 24, 2020, 07:48 UTC
Message-ID: <CAMP44s31OqnRnMO3bcO43VyUCP27o8UGPA5ognGi1s8Se+CRiw@mail.gmail.com>
In-Reply-To: <X7y0GbBQa0a5Alh0@coredump.intra.peff.net>

On Tue, Nov 24, 2020 at 1:19 AM Jeff King <peff@peff.net> wrote:

Show 19 quoted lines

>
> On Mon, Nov 23, 2020 at 09:41:05PM -0600, Felipe Contreras wrote:
>
> > What we really need is something like:
> >
> > 1. git pull # fail by default unless it's a fast-forward
> > 2. git pull --merge # force a merge (unless it's a fast-forward,
> > depending on pull.ff)
> > 3. git pull --rebase # force a rebase (unless it's a fast-forward,
> > depending on pull.ff)
> >
> > Therefore, what we really want is "git pull --rebase" *ignore*
> > "pull.ff=only" (a possible default) or ignore "pull.rebase=ff-only"
> > (also another possible default).
>
> Yep. After reading the first half of your mail, I started to respond
> with the exact same thing. The key thing is letting the command-line
> options override all of the related config. But I guess after reading to
> the end that you don't actually like this. ;)

Yes, the command-line options should override the configuration, and the configuration should override the default.

I'm not sure what makes you think I wouldn't like that.

> I do agree it would be more clear in the long run with a single option
> (config and command-line) that makes it clear the values are mutually
> exclusive. I'm just not sure if it's painful to get there without
> breaking compatibility or introducing confusion in the meantime.

I think it is possible. I did the patches several years ago. And I'm working on the patches right now. We'll see.

Show 20 quoted lines

> > It would be possible to do something like:
> >
> >   if (!opt_rebase && (!opt_ff || !strcmp(opt_ff, "--ff-only")))
> >     turn_default_behavior = 1;
> >
> > But then how would we distinguish between "git pull", and "git pull
> > --no-rebase" (aka. "git pull --merge" / "pull.rebase=false")?
>
> I'm not sure what you mean. We can tell the difference between those
> based on what we saw on the command-line option. I.e., your
> "!opt_rebase" is really a tri-state, which allows something like:
>
>   if (opt_rebase == REBASE_UNSET) {
>           if (opt_ff == FF_UNSET)
>                   opt_ff = ff_default; /* from config or baked-in */
>           }
>           opt_rebase = rebase_default;
>   }
>
> but I didn't look at the logic in git-pull.

Well, in git-pull there's a callback called: parse_opt_rebase(), and if no argument is passed, then it returns REBASE_FALSE (0).

The rest of the code assumes 0 is no-rebase (i.e. merge).

There's no REBASE_UNSET.

Granted, it may be possible to change all the code, introduce a REBASE_UNSET, and make it so 0 is not REBASE_FALSE, and so on. Additionally, the code that deals with the configuration part needs to be changed too.

I'd rather not.

Show 12 quoted lines

> > This is just too much unnecessary complication There's no need to
> > entertain a dozen possible heuristics to avoid "pull.mode", none of
> > which avoid breaking existing behavior.
> >
> > Let's just accept we need push.mode, and then we can have everything:
> > default, ff-only, merge, rebase.
>
> I think it could be possible for the documentation to make clear the
> interactions, especially if the feature is designed with eventual
> deprecation of other options (e.g., if it says "pull.mode=ff-only" means
> that pull.ff won't be examined, and there's no need to ever use it
> anymore).

I'm not sure there will be no need for "pull.ff". Even with "pull.mode=ff-only", you should be able to do "git pull --merge" (should override the configured mode), in which case pull.ff will be considered (and maybe in "git pull --rebase" too).

Regarding the documentation; I think it should be possible to describe the interactions clearly, but as a sequence of overrides, and when no override is specified (default) do something sensible (which right now it's quite complex to determine).

Cheers.

-- 
Felipe Contreras