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From: Junio C Hamano <junkio@cox.net>
Subject: Re: Use a *real* built-in diff generator
Date: Fri, 24 Mar 2006 22:54:10 -0800
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To: Linus Torvalds <torvalds@osdl.org>
In-Reply-To: <Pine.LNX.4.64.0603241938510.15714@g5.osdl.org> (Linus Torvalds's
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Linus Torvalds <torvalds@osdl.org> writes:

> This uses a simplified libxdiff setup to generate unified diffs _without_ 
> doing  fork/execve of GNU "diff".

Good stuff.

> Now, in the interest of full disclosure, I should also point out a few 
> downsides:
>
>  - the libxdiff algorithm is different,...
>
>  - GNU diff does some nice eye-candy, like trying to figure out what the 
>    last function was, and adding that information to the "@@ .." line. 
>    libxdiff doesn't do that. 

That's kind of sad --- Documentation/SubmittingPatches request
people to say "diff -u -p".

>  - The libxdiff thing has some known deficiencies. In particular, it gets 
>    the "\No newline at end of file" case wrong. So this is currently for 
>    the experimental branch only. I hope Davide will help fix it.

Another thing I noticed is that while libxdiff always shows full
line counts "-n,m +l,k" GNU seems to omit them when it can (m,k
<=1).  I am not sure if apply.c is set up to grok what libxdiff
emits correctly.  Running t/t1200 shows some obvious examples.