Re: `git diff`/`git apply` can generate/apply ambiguous hunks (ie. in the wrong place) (just like gnu diff/patch)

From: Emanuel Attila Czirai <corre.a.buscar@gmail.com>
Date: Jul 3, 2024, 16:22 UTC
Message-ID: <CAFjaU5vvk-nNLvCyXAgU9C3ScKBNRPFB7=1PXejmLZi+r7EbNQ@mail.gmail.com>
In-Reply-To: <082b01dacd61$81174a80$8345df80$@nexbridge.com>

Show 16 quoted lines

> >I consider that I don't know enough to understand how `git diff`/`git apply` works
> >internally (and similarly, gnu `diff`/`patch`) to actually change them and make them
> >generate unambiguous hunks where only the hunks that would've been ambiguous
> >have increased context size, instead of the whole patch have increased context size
> >for all hunks(which is what I did for `diffy` too so far, in that proof of concept patch),
> >therefore if a "fix" is deemed necessary(it may not be, as I might've missed
> >something and I'm unaware of it, so a fix may be messing other things up, who
> >knows?!) then I hope someone much more knowledgeable could implement
> >it(maybe even for gnu diff/patch too), and while I don't think that a "please" would
> >be enough, I'm still gonna say it: please do so, if so inclined.
> >
> >Thank you for your time and consideration.
>
> You make good points, but Rust code should not be put into the main git code base as it will break many non-GNU platforms. Perhaps rewriting it is C to be compatible with the git code-base.
> --Randall
>

Ah, definitely whoever writes the fix would do it in C for the git code base, I didn't mean to imply it would be or should be done in rust, therefore please excuse my failure to communicate that clearly. The `diffy` proof-of-concept patch, is just for `diffy`, in rust, and it's just to show a way this could be done and that "it works" that way. It was easier for me to do it for `diffy` in rust, than in C for git diff/apply or gnu diff/patch. If a fix is to be implemented for `git diff/apply`, it would definitely not be in rust by any means, but C, as you mentioned. Thank you for your reply.

Also, I notice that I made a mistake when pasting the patch with the context length of 4, it was a real patch not the one I used in the examples, here's the corrected unambiguous patch: ```diff --- original +++ modified

@@ -1114,8 +1114,12 @@
                     self.config.shell().warn(msg)?
                 }
             }
         }
+        if seen_any_warnings {
+            //comment
+            bail!("reasons");
+        }
         Ok(())
     }

     pub fn set_target_dir(&mut self, target_dir: Filesystem) {
```

Cheers, have a great day everyone!