Re: [PATCH] --color-words: Make the word characters configurable

From: Junio C Hamano <gitster@pobox.com>
Date: May 3, 2008, 17:43 UTC
Message-ID: <7vmyn7uvut.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <alpine.DEB.1.00.0805031501290.30431@racer>

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

Show 8 quoted lines

> Now, you can specify which characters are to be interpreted as word 
> characters with "--color-words=A-Za-z", or by setting the config variable 
> diff.wordCharacters.
>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
>
> 	I would have preferred an approach like this.

Hmmm...

Show 10 quoted lines

> diff --git a/README b/README
> index 548142c..0e325e2 100644
> --- a/README
> +++ b/README
> @@ -4,7 +4,7 @@
>  
>  ////////////////////////////////////////////////////////////////
>  
> -"git" can mean anything, depending on your mood.
> +"git" cann mean anything, depending on your mood.

Heh.

Show 8 quoted lines

> @@ -456,7 +514,7 @@ static void diff_words_show(struct diff_words_data *diff_words)
>  	plus.ptr = xmalloc(plus.size);
>  	memcpy(plus.ptr, diff_words->plus.text.ptr, plus.size);
>  	for (i = 0; i < plus.size; i++)
> -		if (isspace(plus.ptr[i]))
> +		if (!word_character[(unsigned char)plus.ptr[i]])
>  			plus.ptr[i] = '\n';
>  	diff_words->plus.current = 0;

I do not think there is much difference between specifying the set of word characters and the set of non-word characters, especially as long as your definition of "character" is limited to 8-bit bytes. By enumerating word characters, your patch is letting the user specify non word characters that are remainder from the 256-element set. By the way, I think you meant to do the same for the "minus" side a few lines above this hunk.

I commented on the patch from Ping earier about a quite different issue. I was wondering if we can avoid losing the non-word character information. The original code replaces any isspace byte with LF, but a whitespace is a whitespace is a whitespace so there won't be much loss of information, but making the above isspace() configurable means that now you are going to drop non-space non-word characters from the output set.

Instead of dropping the original character and replacing it with LF, I thought a more sensible approach would be to _insert_ a line break between runs of word characters and non-word characters (while probably dropping a LF in the original). That is, instead of what the current implementation of the above loop does to "ab c d" (i.e. rewrite it to "ab\n\nc\nd"), rewrite it to "ab\n \nc\n \nd". Which feels more consistent with the way how \b should work.