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

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

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.

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...

> > That problem whoever, is orthogonal to this series.
> > 
> >> Does this change affect 'am/apply -3'? - Do they still read the config
> >> setting properly?
> > 
> > Good question. I'll have to add more tests to make sure that works
> > properly.

here.

-- 
Felipe Contreras