Re: [PATCH] diff: ignore unmerged paths outside prefix with --relative --cached

[Junio C Hamano <gitster@pobox.com>]

Jeff King <peff@peff.net> writes:

> A diff using --relative ignores entries outside the current directory.
> This results in a segfault when we try to process an unmerged entry
> that's outside of our prefix, since we end up with a NULL diff_filepair
> and use it without checking that it's valid.
> ...
> +cc Junio, as you may have some wisdom on that further exploration.

Will take a look at the history myself, but I would probably not
have much wisdom on a change from 2011.  I often do not even
remember what I ate for breakfast yesterday ;-).

>  diff-lib.c               | 2 +-
>  t/t4045-diff-relative.sh | 9 +++++++++
>  2 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/diff-lib.c b/diff-lib.c
> index ae91027a02..a23119b852 100644
> --- a/diff-lib.c
> +++ b/diff-lib.c
> @@ -467,7 +467,7 @@ static void do_oneway_diff(struct unpack_trees_options *o,
>  	if (cached && idx && ce_stage(idx)) {
>  		struct diff_filepair *pair;
>  		pair = diff_unmerge(&revs->diffopt, idx->name);
> -		if (tree)
> +		if (pair && tree)
>  			fill_filespec(pair->one, &tree->oid, 1,
>  				      tree->ce_mode);
>  		return;
> diff --git a/t/t4045-diff-relative.sh b/t/t4045-diff-relative.sh
> index 2c8493fe66..167be0bdcc 100755
> --- a/t/t4045-diff-relative.sh
> +++ b/t/t4045-diff-relative.sh
> @@ -245,4 +245,13 @@ test_expect_failure 'diff --relative with change in subdir' '
>  	test_cmp expected out
>  '
>  
> +test_expect_success 'diff --relative --cached with change in subdir' '
> +	git switch br3 &&
> +	test_when_finished "git merge --abort" &&
> +	test_must_fail git merge sub1 &&
> +	echo file0 >expected &&
> +	git -C subdir diff --relative --name-only --cached >out &&
> +	test_cmp expected out
> +'
> +
>  test_done