Re: [PATCH 4/7] checkout: fix merge.conflictstyle handling

> On 10/06/2021 17:32, Felipe Contreras wrote:
> > Phillip Wood wrote:
> >> On 10/06/2021 15:11, Felipe Contreras wrote:
> >>> Phillip Wood wrote:
> >>>> On 09/06/2021 20:28, Felipe Contreras wrote:
> >>>>> Currently both merge.conflictStyle and `git commit --merge
> >>>>> --conflict=diff3` don't work together, since the former wrongly
> >>>>> overrides the later.
> >>>>>
> >>>>> The way merge configurations are handled is not correct.
> >>>>> It should be possible to do git_config(merge_recursive_config, ...) just
> >>>>> like we can with git_diff_basic_config and others.
> >>>>
> >>>> It would be helpful to explain what the problem with
> >>>> merge_recursive_config() actually is rather than just saying "it should
> >>>> be possible ..."
> >>>
> >>> The problem is that you can't do this:
> >>>
> >>>     git_config(merge_recursive_config, NULL);
> >>>
> >>> As it was explained.
> >>
> >> You do not explain why you cannot do that
> > 
> >    % git grep merge_recursive_config
> >    static void merge_recursive_config(struct merge_options *opt)
> > 
> > For starters it's a static function.
> > 
> > Second, clearly the type of functions git_config() receives are not
> > `void (*)(struct merge_options *)`.
> > 
> > I mean, I do see value in explaning as much detail as needed in the
> > commit message, but it shouldn't be a lesson on git's codebase:
> > git_config() is a standard thing, and it's even mentioned in the user
> > manual.
> 
> I'm not asking for a lesson on git's config system, I'm asking you to 
> add a sentence to the commit message to explain what the problem is 
> rather than just saying "you should be able to do this but you can't".

> > https://git-scm.com/docs/user-manual#birdview-on-the-source-code
> > 
> >>> That is the problem. I don't know how that's not clear.
> >>>
> >>>>> Therefore builtins like `git merge` can't call this function at the
> >>>>> right time.
> >>>>    >
> >>>>> We shuffle the functions a little bit so at least merge_recursive_config
> >>>>> doesn't call git_xmerge_config directly and thus override previous
> >>>>> configurations.
> >>>>
> >>>> Rather than papering of the problem, how difficult would it be to add a
> >>>> field to ll_merge_options and pass the conflict style with that rather
> >>>> than fiddling with the order that we set a global variable.
> >>>
> >>> Probably not that difficult, but then we also need a parser that
> >>> converts from "diff3" to whatever values we decide in that new field. We
> >>> would need a new parse_config_conflict_style() function.
> >>> And that function will be only used by `git checkout` and nothing else.
> >>> So I don't think there's much value in it.
> >>
> >> It would allow us to add a --conflict option to all the mergey commands
> >> in the future and would be much easier to reason about than the approach
> >> of juggling where we call git_xmerge_config().
> > 
> > Feel free to write a patch for that.
> > 
> >> This patch requires us to audit all the code paths that end up in
> >> merge_recursive_config() to make sure they now call
> >> git_xmerge_config() themselves. You don't seem to have done that as
> >> you don't know if am/apply are affected or not.
> > 
> > That is a separate issue, that I already mentioned...
> 
> I know you are going to add some tests but the point is that when making 
> a change like this you need to actively audit all the callers of 
> init_merge_options() and ensure that they are now calling 
> git_config(git_xmerge_config) and base you tests on what you find while 
> doing that.