Re: [PATCH] apply: fix new-style empty context line triggering incomplete-line check

> A new-style unified context diff represents an empty context line
> with an empty line (instead of a line with a single SP on it).  The
> code to check whitespace errors in an incoming patch is designed to
> omit the first byte of a line (typically SP, "-", or "+") and pass the
> remainder of the line to the whitespace checker.
>
> Usually we do not pass a context line to the whitespace error checker,
> but when we are correcting errors, we do.  This "remove the first
> byte and send the remainder" strategy of checking a line ended up
> sending a zero-length string to the whitespace checker when seeing a
> new-style empty context line, which caused the whitespace checker to
> say "ah, you do not even have a newline at the end!", leading to an
> "incomplete line" in the middle of the patch!
>
> Fix this by pretending that we got a traditional empty context line
> when we drive the whitespace checker.
>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
>  apply.c                  | 12 ++++++++++--
>  t/t4124-apply-ws-rule.sh | 16 ++++++++++++++++
>  2 files changed, 26 insertions(+), 2 deletions(-)

> diff --git a/apply.c b/apply.c
> index f01204d15b..e88e5c77e3 100644
> --- a/apply.c
> +++ b/apply.c
> @@ -1796,8 +1796,16 @@ static int parse_fragment(struct apply_state *state,
>  			trailing++;
>  			check_old_for_crlf(patch, line, len);
>  			if (!state->apply_in_reverse &&
> -			    state->ws_error_action == correct_ws_error)
> -				check_whitespace(state, line, len, patch->ws_rule);
> +			    state->ws_error_action == correct_ws_error) {
> +				const char *test_line = line;
> +				int test_len = len;
> +				if (*line == '\n') {
> +					test_line = " \n";
> +					test_len = 2;
> +				}
> +				check_whitespace(state, test_line, test_len,
> +						 patch->ws_rule);
> +			}
>  			break;
>  		case '-':
>  			if (!state->apply_in_reverse)
> diff --git a/t/t4124-apply-ws-rule.sh b/t/t4124-apply-ws-rule.sh
> index 29ea7d4268..8573e12f46 100755
> --- a/t/t4124-apply-ws-rule.sh
> +++ b/t/t4124-apply-ws-rule.sh
> @@ -561,6 +561,22 @@ test_expect_success 'check incomplete lines (setup)' '
>  	git config core.whitespace incomplete-line
>  '
>  
> +test_expect_success 'no incomplete context line (not an error)' '
> +	test_when_finished "rm -f sample*-i patch patch-new target" &&
> +	(test_write_lines 1 2 3 "" 4 5 ) >sample-i &&
> +	(test_write_lines 1 2 3 "" 0 5 ) >sample2-i &&
> +	cat sample-i >target &&
> +	git add target &&
> +	cat sample2-i >target &&
> +	git diff-files -p target >patch &&
> +	sed -e "s/^ $//" <patch >patch-new &&
> +
> +	cat sample-i >target &&
> +	git apply --whitespace=fix <patch-new 2>error &&
> +	test_cmp sample2-i target &&
> +	test_must_be_empty error
> +'
> +
>  test_expect_success 'incomplete context line (not an error)' '
>  	(test_write_lines 1 2 3 4 5 && printf 6) >sample-i &&
>  	(test_write_lines 1 2 3 0 5 && printf 6) >sample2-i &&