Re: git apply --3way behaves abnormally when the patch contains binary changes.

>
> Jerry Zhang <jerry@skydio.com> writes:
>
> >>         # 2. based on left_bin branch, make any change, and commit
> >>         git checkout -b right &&
> >>         cat bin.png bin.png > bin.png &&
> >>         git add bin.png &&
> >>         git commit -m "update binary file" &&
> >>
> >>         # 3. make patch
> >>         git diff --binary left..right >bin.diff &&
> >>         # apply --3way, and it will fail
> >>         test_must_fail git apply --index --3way bin.diff
> >> '
> >> "
> >>
> >> But  "git apply --index --3way bin.diff" will not faill on Git version 2.31.0.
> > Are you sure? I checked out to "commit
> > a5828ae6b52137b913b978e16cd2334482eb4c1f (HEAD, tag: v2.31.0)" and
> > rebuilt and ran your test snippet and it still failed.
>
> Isn't it just because the reproduction recipe is simply wrong?
>
> It says
>
>     * be on left branch and have a binary file
>     * be on right branch and have a modified binary file
>     * create a patch to take left to right
>
> Notice that we have a patch and we are still on the right branch.
> Of course, applying the patch to take us from left to right would
> fail from that state, but I _think_ the intent of the reproduction
> recipe was, after all of the above, do this here:
>
>     * switch to left branch and attempt to apply the patch.
>
> And the patch is meant to take us from left to right, and we are on
> pristine left, the application ought to cleanly succeed, no?
>
> "git apply bin.diff" would probably work correctly but I do not know
> offhand what the code after your change does with --3way enabled.
>
> We refuse to merge binary files, so I would not be surprised if we
> failed the 3way in this case (even though we _could_ fast-forward,
> it may not be worth complicating the --3way logic---nobody sane
> would say --3way when it is unnecessary) but after 3way fails, do we
> still correctly fall back to "straight application" like we do for
> text patches with your change?  Before your change, we would have
> first attempted the "straight application", which would succeed and
> wouldn't have hit "3way will refuse to merge binaries" at all.

>
> So, I do not think it is implausible that we are seeing a legit
> regression report.
>
> Thanks.