Re: [PATCH] gitattributes: Cover Objective-C source files

[Akihiko Odaki]

On 2022/03/19 22:49, Philippe Mathieu-Daudé wrote:
> On 19/3/22 04:25, Akihiko Odaki wrote:
> > On 2022/03/19 1:14, Philippe Mathieu-Daudé wrote:
> > > > Commit 29cf16db23 says:
> > > > > Since commits 0979ed017f0 ("meson: rename .inc.h files to .h.inc")
> > > > > and 139c1837db7 ("meson: rename included C source files to .c.inc")
> > > > > 'git-diff --function-context' stopped displaying C function context
> > > > > correctly.
> > > >
> > > > So I suspect Git has some knowledge of common file extensions like 
> > > > .c, .h and .m although I couldn't find in the source code of Git.
> > >
> > > 'git-diff --function-context' doesn't work for me without this change.
> >
> > With some debugging, I found Apple's Git distribution actually carries 
> > a default gitattributes file which annotates *.m.
> > https://github.com/apple-opensource/Git/blob/master/gitattributes
>
> I see, I'm using the Homebrew git. Anyway this change helps non-native
> Darwin users to review these .m files.
>
> > However, it does not annotate *.c or *.h. Apparently there is no "c" 
> > diff pattern and they are handled with the "default" diff pattern 
> > which is actually designed for C. In fact, "c" diff pattern is not 
> > present in the documentation:
> > https://git-scm.com/docs/gitattributes#_defining_an_external_diff_driver
>
> 'cpp' is listed. Maybe 'c' is aliased to it?

I don't think so. The string 'cpp' is rare in Git code base and I still 
couldn't find such code.

> > In conclusion, *.m should be listed in gitattributes but *.c.inc and 
> > *.h.inc should not be if my understanding is correct.
>
> But then how git-tools can detect .inc are C files? I remember it was
> not working (on Linux hosts) without this change.

It doesn't have to. If files are not listed in gitattributes, it simply 
applies the "default" diff pattern, which works with C.

I can confirm removing *.c.inc and *.h.inc from gitattributes does not 
affect the output of git diff -W on git version 2.35.1 which comes with 
Fedora.

Regards,
Akihiko Odaki

> > Paolo Bonzini, I found you are the author of commit 29cf16db23. Can 
> > you test the above conclusion?
> >
> > Regards,
> > Akihiko Odaki