Subject: Re: [PATCH v4 2/2] format-patch: teach format.notes config option

From: Denton Liu <[email-masked]>
Date: Mon, 9 Dec 2019 00:24:51 -0800

Hi Elijah,

On Sat, Dec 07, 2019 at 11:48:59PM -0800, Elijah Newren wrote:
> > @@ -864,6 +866,22 @@ static int git_format_config(const char *var, const char *value, void *cb)
> >                         from = NULL;
> >                 return 0;
> >         }
> > +       if (!strcmp(var, "format.notes")) {
> > +               struct strbuf buf = STRBUF_INIT;
> > +               int b = git_parse_maybe_bool(value);
> > +               if (!b)
> > +                       return 0;
> > +               rev->show_notes = 1;
> > +               if (b < 0) {
> > +                       strbuf_addstr(&buf, value);
> > +                       expand_notes_ref(&buf);
> > +                       string_list_append(&rev->notes_opt.extra_notes_refs,
> > +                                       strbuf_detach(&buf, NULL));
> > +               } else {
> > +                       rev->notes_opt.use_default_notes = 1;
> > +               }
> > +               return 0;
> > +       }
> 
> What if someone has multiple format.notes entries in their config
> file, but the last entry is "false" -- shouldn't that disable notes?
> Also, what if they specify both "true" and e.g.
> "refs/notes/my-cool-notes"?  In that case, should it show
> refs/notes/my-cool-notes because that's obviously showing some notes
> so it satisfies true as well as the specific request about which note,
> or should it treat "true" the same as the-default-notes-ref and then
> add the two refs together and show them both?

I think I'll just copy the existing logic of --notes, --notes=<ref> and
--no-notes from revision.c to `format.notes = true`, 
`format.notes = <ref>` and `format.notes = false` respectively. IOW,
with `format.notes = true`, we'll unconditionally use the default notes,
with `format.notes = <ref>`, we'll append <ref> to the reflist and with
`format.notes = false`, we'll clear and unset the notes refs.

It seems like that logic has been around for almost a decade and I don't
think anyone's complained about it so I think it should be safe to
duplicate.

> 
> >
> >         return git_log_config(var, value, cb);
> >  }
> > @@ -1617,8 +1635,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
> >         extra_to.strdup_strings = 1;
> >         extra_cc.strdup_strings = 1;
> >         init_log_defaults();
> > -       git_config(git_format_config, NULL);
> >         repo_init_revisions(the_repository, &rev, prefix);
> > +       git_config(git_format_config, &rev);
> 
> Calling git_config() after repo_init_revisions() breaks things;
> generally git_config() should always be called first.  Here,
> git_format_config() can set up parameters used by
> repo_init_revisions(), and by reversing the order of the two you end
> up ignoring settings specified by the user (e.g. diff.context having a
> value of 5).  This came up due to the bug report at
> https://lore.kernel.org/git/[email-masked]/T/#mb6a09958ff10acde295b37a9136bc3791fd4a2c2
> (though fixing the issue there _also_ requires fixing git_am_config()
> to call git_diff_ui_config()).  To break the circular dependency here,
> we'd need to store the information that git_format_config() discovers
> in some data structure besides rev, and then after the
> repo_init_revisions() call has finished then update rev.

I see, I'll move the git_config() back up while I'm at it.

> 
> I was just going to do that, but then ran into the questions above
> about multiple format.notes entries in the config file, and am not as
> sure about what should be done about that stuff (and I don't want to
> try to translate the current behavior as-is while tweaking where the
> stuff is stored, both because I'm not sure of the right behavior and
> because I don't want future folks to blame the code to me when they
> hit bugs in this area), so I'm firing off this email instead.

Sounds good, I don't want my bugs blamed on anyone else either ;)

I'll try to get a patchset out soon and hopefully you'll be able to base
your work off of that.

Thanks,

Denton

> So, um...help?
> Thanks,
> Elijah