Re: [PATCH 2/2] add--interactive: detect bogus diffFilter output

> It's important that the diff-filter only filter the
> individual lines, and that there remain a one-to-one mapping
> between the input and output lines. Otherwise, things like
> hunk-splitting will behave quite unexpectedly (e.g., you
> think you are splitting at one point, but it has a different
> effect in the text patch we apply).
>
> We can't detect all problematic cases, but we can at least
> catch the obvious case where we don't even have the correct
> number of lines.

>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
>  git-add--interactive.perl  | 8 ++++++++
>  t/t3701-add-interactive.sh | 8 ++++++++
>  2 files changed, 16 insertions(+)
>
> diff --git a/git-add--interactive.perl b/git-add--interactive.perl
> index 964c3a7542..ff02008abe 100755
> --- a/git-add--interactive.perl
> +++ b/git-add--interactive.perl
> @@ -705,6 +705,14 @@ sub parse_diff {
>  	}
>  	my (@hunk) = { TEXT => [], DISPLAY => [], TYPE => 'header' };
>  
> +	if (@colored && @colored != @diff) {
> +		print STDERR
> +		  "fatal: mismatched output from interactive.diffFilter\n",
> +		  "hint: Your filter must maintain a one-to-one correspondence\n",
> +		  "hint: between its input and output lines.\n";
> +		exit 1;
> +	}
> +
>  	for (my $i = 0; $i < @diff; $i++) {
>  		if ($diff[$i] =~ /^@@ /) {
>  			push @hunk, { TEXT => [], DISPLAY => [],
> diff --git a/t/t3701-add-interactive.sh b/t/t3701-add-interactive.sh
> index 64fe56c3d5..9bb17f91b2 100755
> --- a/t/t3701-add-interactive.sh
> +++ b/t/t3701-add-interactive.sh
> @@ -404,6 +404,14 @@ test_expect_success TTY 'diffFilter filters diff' '
>  	grep foo:.*content output
>  '
>  
> +test_expect_success TTY 'detect bogus diffFilter output' '
> +	git reset --hard &&
> +
> +	echo content >test &&
> +	test_config interactive.diffFilter "echo too-short" &&
> +	printf y | test_must_fail test_terminal git add -p
> +'
> +
>  test_expect_success 'patch-mode via -i prompts for files' '
>  	git reset --hard &&