Re: Mark trailing whitespace error in del lines of diff

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

Junio C Hamano <gitster@pobox.com> writes:

> I'll send out two patch series to do the painting part (I didn't
> want to touch "--check", as its utility is even more dubious
> compared to painting, at least to me).

And here is the second one.

-- >8 --
Subject: [PATCH 2/2] diff.c: --ws-check-deleted option

Traditionally, we only cared about whitespace breakages introduced
in new lines.  Some people want to paint whitespace breakages on old
lines, too.  When they see a whitespace breakage on a new line, they
can spot the same kind of whitespace breakage on the corresponding
old line and want to say "Ah, that breakage is there but was
inherited from the original, so let's not fix that for now."

Enable such use with the new option, "--ws-check-deleted".

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/diff-options.txt |  7 +++++++
 diff.c                         | 21 ++++++++++++++++++++-
 diff.h                         |  1 +
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index b7c3afe..617cbc6 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -282,6 +282,13 @@ ifndef::git-format-patch[]
 	initial indent of the line are considered whitespace errors.
 	Exits with non-zero status if problems are found. Not compatible
 	with --exit-code.
+
+--ws-check-deleted::
+--no-ws-check-deleted::
+	Highlight whitespace errors in deleted lines in the color
+	specified by `color.diff.whitespace`, as well as in added
+	lines.
+
 endif::git-format-patch[]
 
 --full-index::
diff --git a/diff.c b/diff.c
index 93c1eb4..44cc234 100644
--- a/diff.c
+++ b/diff.c
@@ -503,8 +503,22 @@ static void emit_del_line(const char *reset,
 			  const char *line, int len)
 {
 	const char *set = diff_get_color(ecbdata->color_diff, DIFF_FILE_OLD);
+	const char *ws = NULL;
 
-	emit_line_0(ecbdata->opt, set, reset, '-', line, len);
+	if (ecbdata->opt->ws_check_deleted) {
+		ws = diff_get_color(ecbdata->color_diff, DIFF_WHITESPACE);
+		if (!*ws)
+			ws = NULL;
+	}
+
+	if (!ws)
+		emit_line_0(ecbdata->opt, set, reset, '-', line, len);
+	else {
+		/* Emit just the prefix, then the rest. */
+		emit_line_0(ecbdata->opt, set, reset, '-', "", 0);
+		ws_check_emit(line, len, ecbdata->ws_rule,
+			      ecbdata->opt->file, set, reset, ws);
+	}
 }
 
 static void emit_hunk_header(struct emit_callback *ecbdata,
@@ -3819,6 +3833,11 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	else if (skip_prefix(arg, "--submodule=", &arg))
 		return parse_submodule_opt(options, arg);
 
+	else if (!strcmp(arg, "--ws-check-deleted"))
+		options->ws_check_deleted = 1;
+	else if (!strcmp(arg, "--no-ws-check-deleted"))
+		options->ws_check_deleted = 0;
+
 	/* misc options */
 	else if (!strcmp(arg, "-z"))
 		options->line_termination = 0;
diff --git a/diff.h b/diff.h
index f6fdf49..baca5ec 100644
--- a/diff.h
+++ b/diff.h
@@ -138,6 +138,7 @@ struct diff_options {
 	int dirstat_permille;
 	int setup;
 	int abbrev;
+	int ws_check_deleted;
 	const char *prefix;
 	int prefix_length;
 	const char *stat_sep;
-- 
2.4.1-511-gc1146d5