Re: [PATCH v5 2/3] add -p: gracefully handle unparseable hunk headers in colored diffs

[Phillip Wood <phillip.wood123@gmail.com>]

Hi Dscho

On 01/09/2022 16:42, Johannes Schindelin via GitGitGadget wrote:
> From: Johannes Schindelin <johannes.schindelin@gmx.de>
> 
> In
> https://lore.kernel.org/git/ecf6f5be-22ca-299f-a8f1-bda38e5ca246@gmail.com,
> Phillipe Blain reported that the built-in `git add -p` command fails
> when asked to use [`diff-so-fancy`][diff-so-fancy] to colorize the diff.
> 
> The reason is that this tool produces colored diffs with a hunk header
> that does not contain any parseable `@@ ... @@` line range information,
> and therefore we cannot detect any part in that header that comes after
> the line range.
> 
> As proposed by Phillip Wood, let's take that for a clear indicator that
> we should show the hunk headers verbatim. This is what the Perl version
> of the interactive `add` command did, too.
> 
> [diff-so-fancy]: https://github.com/so-fancy/diff-so-fancy
> 
> Reported-by: Philippe Blain <levraiphilippeblain@gmail.com>
> Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---

> @@ -659,6 +659,15 @@ static void render_hunk(struct add_p_state *s, struct hunk *hunk,
>   		if (!colored) {
>   			p = s->plain.buf + header->extra_start;
>   			len = header->extra_end - header->extra_start;
> +		} else if (header->suppress_colored_line_range) {
> +			strbuf_add(out,
> +				   s->colored.buf + header->colored_extra_start,
> +				   header->colored_extra_end -
> +				   header->colored_extra_start);
> +
> +			strbuf_add(out, s->colored.buf + hunk->colored_start,
> +				   hunk->colored_end - hunk->colored_start);
> +			return;

Having an extra branch for this that returns early makes it easy to see 
what is being printed when we cannot parse the hunk header.

> diff --git a/t/t3701-add-interactive.sh b/t/t3701-add-interactive.sh
> index 8a594700f7b..a94e7c53c8a 100755
> --- a/t/t3701-add-interactive.sh
> +++ b/t/t3701-add-interactive.sh
> @@ -767,6 +767,16 @@ test_expect_success 'detect bogus diffFilter output' '
>   	grep "mismatched output" output
>   '
>   
> +test_expect_success 'handle iffy colored hunk headers' '
> +	git reset --hard &&
> +
> +	echo content >test &&
> +	printf n >n &&
> +	force_color git -c interactive.diffFilter="sed s/.*@@.*/XX/" \
> +		add -p >output 2>&1 <n &&
> +	grep "^XX$" output

We check that the hunk header line from filtered diff was reproduced 
verbatim

This all looks good to me

Best Wishes

Phillip