Re: [PATCH V2] patch-id: fix scan_hunk_header on diffs with 1 line of before/after

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

Jerry Zhang <jerry@skydio.com> writes:

> Normally diffs will contain a hunk header of the format
> "@@ -2,2 +2,15 @@ code". However in certain situations git can
> omit the second comma separated value in either before or after
> line counts in the case where there is only one line.
>
> This can produce hunk headers that look like
> "@@ -2 +2,18 @@ code" or "@@ -2,2 +2 @@ code".
> As a result, scan_hunk_header mistakenly returns the line
> number as line count, which then results in unpredictable
> parsing errors with the rest of the patch, including giving
> multiple lines of output for a single commit.
>
> Fix by explicitly setting line count to 1 when there is
> no comma, and add a test.
>
> apply.c contains this same logic except it is correct. A
> worthwhile future project might be to unify these two diff
> parsers so they both benefit from fixes.
>
> Signed-off-by: Jerry Zhang <jerry@skydio.com>
> ---
> V1->V2:
> - Removed references to -U1 since this isn't limited to that
> - Added notes for future tasks
>
>  builtin/patch-id.c  |  9 +++++++--
>  t/t4204-patch-id.sh | 32 +++++++++++++++++++++++++++++++-
>  2 files changed, 38 insertions(+), 3 deletions(-)
>
> diff --git a/builtin/patch-id.c b/builtin/patch-id.c
> index 822ffff51f..881fcf3273 100644
> --- a/builtin/patch-id.c
> +++ b/builtin/patch-id.c
> @@ -30,26 +30,31 @@ static int scan_hunk_header(const char *p, int *p_before, int *p_after)
>  
>  	q = p + 4;
>  	n = strspn(q, digits);
>  	if (q[n] == ',') {
>  		q += n + 1;
> +		*p_before = atoi(q);
>  		n = strspn(q, digits);
> +	} else {
> +		*p_before = 1;
>  	}
> +
>  	if (n == 0 || q[n] != ' ' || q[n+1] != '+')
>  		return 0;
>  
>  	r = q + n + 2;
>  	n = strspn(r, digits);
>  	if (r[n] == ',') {
>  		r += n + 1;
> +		*p_after = atoi(r);
>  		n = strspn(r, digits);
> +	} else {
> +		*p_after = 1;
>  	}
>  	if (n == 0)
>  		return 0;
>  
> -	*p_before = atoi(q);
> -	*p_after = atoi(r);
>  	return 1;
>  }
>  
>  static int get_one_patchid(struct object_id *next_oid, struct object_id *result,
>  			   struct strbuf *line_buf, int stable)
> diff --git a/t/t4204-patch-id.sh b/t/t4204-patch-id.sh
> index 80f4a65b28..34a386aee2 100755
> --- a/t/t4204-patch-id.sh
> +++ b/t/t4204-patch-id.sh
> @@ -36,11 +36,11 @@ test_expect_success 'patch-id output is well-formed' '
>  calc_patch_id () {
>  	patch_name="$1"
>  	shift
>  	git patch-id "$@" >patch-id.output &&
>  	sed "s/ .*//" patch-id.output >patch-id_"$patch_name" &&
> -	test_line_count -gt 0 patch-id_"$patch_name"
> +	test_line_count -eq 1 patch-id_"$patch_name"
>  }
>  
>  get_top_diff () {
>  	git log -p -1 "$@" -O bar-then-foo --
>  }
> @@ -200,6 +200,36 @@ EOF
>  test_expect_success 'patch-id handles no-nl-at-eof markers' '
>  	cat nonl | calc_patch_id nonl &&
>  	cat withnl | calc_patch_id withnl &&
>  	test_cmp patch-id_nonl patch-id_withnl
>  '
> +
> +cat >diffu1 <<\EOF
> +diff --git a/bar b/bar
> +index bdaf90f..31051f6 100644
> +--- a/bar
> ++++ b/bar
> +@@ -2 +2,2 @@
> + b
> ++c
> +diff --git a/car b/car
> +index 00750ed..2ae5e34 100644
> +--- a/car
> ++++ b/car
> +@@ -1 +1,2 @@
> + 3
> ++d
> +diff --git a/foo b/foo
> +index e439850..7146eb8 100644
> +--- a/foo
> ++++ b/foo
> +@@ -2 +2,2 @@
> + a
> ++e
> +EOF
> +
> +test_expect_success 'patch-id handles diffs with one line of before/after'

There is a opening quote for the body missing here.

> +	cat diffu1 | calc_patch_id diffu1 &&
> +	test_config patchid.stable true &&
> +	cat diffu1 | calc_patch_id diffu1stable
> +'
>  test_done