Re: [PATCH 1/1] git-apply: Allow simultaneous --cached and --3way options

[Jerry Zhang <jerry@skydio.com>]

On Fri, Apr 2, 2021 at 8:46 PM Elijah Newren <newren@gmail.com> wrote:
>
> I'm not that familiar with apply.c, but let me attempt to take a look...
>
> On Fri, Apr 2, 2021 at 6:36 PM Jerry Zhang <jerry@skydio.com> wrote:
> >
> > Previously, --cached and --3way were not
> > allowed to be used together, since --3way
> > wrote conflict markers into the working tree.
> >
> > These changes change semantics so that if
> > these flags are given together and there is
> > a conflict, the conflict markers are added
> > directly to cache. If there is no conflict,
> > the patch is applied directly to cache as
> > expected.
> >
> > Signed-off-by: Jerry Zhang <jerry@skydio.com>
> > Signed-off-by: Jerry Zhang <jerryxzha@googlemail.com>
> > ---
> >  Documentation/git-apply.txt |  4 +++-
> >  apply.c                     | 13 +++++++------
> >  2 files changed, 10 insertions(+), 7 deletions(-)
> >
> > diff --git a/Documentation/git-apply.txt b/Documentation/git-apply.txt
> > index 91d9a8601c..3dc0085066 100644
> > --- a/Documentation/git-apply.txt
> > +++ b/Documentation/git-apply.txt
> > @@ -89,7 +89,9 @@ OPTIONS
> >         and we have those blobs available locally, possibly leaving the
> >         conflict markers in the files in the working tree for the user to
> >         resolve.  This option implies the `--index` option, and is incompatible
> > -       with the `--reject` and the `--cached` options.
> > +       with the `--reject` option. When used with the --cached option, any
> > +       conflict markers are added directly to the cache rather than the
> > +       working tree.
> >
> >  --build-fake-ancestor=<file>::
> >         Newer 'git diff' output has embedded 'index information'
> > diff --git a/apply.c b/apply.c
> > index 6695a931e9..fc94ca0e99 100644
> > --- a/apply.c
> > +++ b/apply.c
> > @@ -133,8 +133,6 @@ int check_apply_state(struct apply_state *state, int force_apply)
> >
> >         if (state->apply_with_reject && state->threeway)
> >                 return error(_("--reject and --3way cannot be used together."));
> > -       if (state->cached && state->threeway)
> > -               return error(_("--cached and --3way cannot be used together."));
> >         if (state->threeway) {
> >                 if (is_not_gitdir)
> >                         return error(_("--3way outside a repository"));
> > @@ -4490,13 +4488,16 @@ static int create_file(struct apply_state *state, struct patch *patch)
> >
> >         if (!mode)
> >                 mode = S_IFREG | 0644;
> > -       if (create_one_file(state, path, mode, buf, size))
> > -               return -1;
> > +       if (!state->cached) {
>
> Why add this check?  create_one_file() already has an early return if
> state->cached is true.
>
removed in latest patch
> > +               if (create_one_file(state, path, mode, buf, size))
> > +                       return -1;
> > +       }
> >
> > -       if (patch->conflicted_threeway)
> > +       if (patch->conflicted_threeway && !state->cached)
> >                 return add_conflicted_stages_file(state, patch);
> > -       else if (state->update_index)
> > +       else if (state->update_index) {
> >                 return add_index_file(state, path, mode, buf, size);
>
> So if something had conflicts, you ignore the various conflicted
> modes, and just add it to the index as it stands.  What if it was
> deleted upstream and modified locally?  Doesn't that just ignore the
> conflict, make it invisible to the user, and add the locally modified
> version?  Similarly if it was renamed upstream and modified locally,
> doesn't that end up in both files being present?  And if there's a
> directory/file conflict, due to the lack of ADD_CACHE_SKIP_DFCHECK (or
> whatever it's called), the add is just going to fail, but perhaps
> that's the most reasonable case as it'd print an error message and
> return -1, I think.
>
> Again, I didn't test any of this out and I'm not so familiar with this
> code, so I'm guessing at these scenarios.  If I'm wrong about how this
> works, the commit message probably deserves an explanation about why
> they work, and we'd definitely need a few testcases for these types of
> scenarios.  If I'm right, the current implementation is problematic at
> least if not the idea of using these options together.
Echoing my other reply, I think I will give up on the conflict markers and
just leave the files at the higher stages. I think that will address any
safety concerns since that's what --3way does without the cached
flag