Merge branch 'jc/diff-ws-error-highlight'

Allow whitespace breakages in deleted and context lines to be also
painted in the output.

* jc/diff-ws-error-highlight:
  diff.c: --ws-error-highlight=<kind> option
  diff.c: add emit_del_line() and emit_context_line()
  t4015: separate common setup and per-test expectation
  t4015: modernise style

4 files changed, 385 insertions, 260 deletions

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 3ad6404dbc..d56ca90998 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -291,6 +291,16 @@ 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-error-highlight=<kind>::
+	Highlight whitespace errors on lines specified by <kind>
+	in the color specified by `color.diff.whitespace`.  <kind>
+	is a comma separated list of `old`, `new`, `context`.  When
+	this option is not given, only whitespace errors in `new`
+	lines are highlighted.  E.g. `--ws-error-highlight=new,old`
+	highlights whitespace errors on both deleted and added lines.
+	`all` can be used as a short-hand for `old,new,context`.
+
 endif::git-format-patch[]
 
 --full-index::
diff --git a/diff.c b/diff.c
index 7500c55095..324be1d959 100644
--- a/diff.c
+++ b/diff.c
@@ -478,26 +478,59 @@ static int new_blank_line_at_eof(struct emit_callback *ecbdata, const char *line
 	return ws_blank_line(line, len, ecbdata->ws_rule);
 }
 
-static void emit_add_line(const char *reset,
-			  struct emit_callback *ecbdata,
-			  const char *line, int len)
+static void emit_line_checked(const char *reset,
+			      struct emit_callback *ecbdata,
+			      const char *line, int len,
+			      enum color_diff color,
+			      unsigned ws_error_highlight,
+			      char sign)
 {
-	const char *ws = diff_get_color(ecbdata->color_diff, DIFF_WHITESPACE);
-	const char *set = diff_get_color(ecbdata->color_diff, DIFF_FILE_NEW);
+	const char *set = diff_get_color(ecbdata->color_diff, color);
+	const char *ws = NULL;
 
-	if (!*ws)
-		emit_line_0(ecbdata->opt, set, reset, '+', line, len);
-	else if (new_blank_line_at_eof(ecbdata, line, len))
+	if (ecbdata->opt->ws_error_highlight & ws_error_highlight) {
+		ws = diff_get_color(ecbdata->color_diff, DIFF_WHITESPACE);
+		if (!*ws)
+			ws = NULL;
+	}
+
+	if (!ws)
+		emit_line_0(ecbdata->opt, set, reset, sign, line, len);
+	else if (sign == '+' && new_blank_line_at_eof(ecbdata, line, len))
 		/* Blank line at EOF - paint '+' as well */
-		emit_line_0(ecbdata->opt, ws, reset, '+', line, len);
+		emit_line_0(ecbdata->opt, ws, reset, sign, line, len);
 	else {
 		/* Emit just the prefix, then the rest. */
-		emit_line_0(ecbdata->opt, set, reset, '+', "", 0);
+		emit_line_0(ecbdata->opt, set, reset, sign, "", 0);
 		ws_check_emit(line, len, ecbdata->ws_rule,
 			      ecbdata->opt->file, set, reset, ws);
 	}
 }
 
+static void emit_add_line(const char *reset,
+			  struct emit_callback *ecbdata,
+			  const char *line, int len)
+{
+	emit_line_checked(reset, ecbdata, line, len,
+			  DIFF_FILE_NEW, WSEH_NEW, '+');
+}
+
+static void emit_del_line(const char *reset,
+			  struct emit_callback *ecbdata,
+			  const char *line, int len)
+{
+	emit_line_checked(reset, ecbdata, line, len,
+			  DIFF_FILE_OLD, WSEH_OLD, '-');
+}
+
+static void emit_context_line(const char *reset,
+			      struct emit_callback *ecbdata,
+			      const char *line, int len)
+{
+	emit_line_checked(reset, ecbdata, line, len,
+			  DIFF_PLAIN, WSEH_CONTEXT, ' ');
+}
+
 static void emit_hunk_header(struct emit_callback *ecbdata,
 			     const char *line, int len)
 {
@@ -603,7 +636,6 @@ static void emit_rewrite_lines(struct emit_callback *ecb,
 {
 	const char *endp = NULL;
 	static const char *nneof = " No newline at end of file\n";
-	const char *old = diff_get_color(ecb->color_diff, DIFF_FILE_OLD);
 	const char *reset = diff_get_color(ecb->color_diff, DIFF_RESET);
 
 	while (0 < size) {
@@ -613,8 +645,7 @@ static void emit_rewrite_lines(struct emit_callback *ecb,
 		len = endp ? (endp - data + 1) : size;
 		if (prefix != '+') {
 			ecb->lno_in_preimage++;
-			emit_line_0(ecb->opt, old, reset, '-',
-				    data, len);
+			emit_del_line(reset, ecb, data, len);
 		} else {
 			ecb->lno_in_postimage++;
 			emit_add_line(reset, ecb, data, len);
@@ -1250,17 +1281,27 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 		return;
 	}
 
-	if (line[0] != '+') {
-		const char *color =
-			diff_get_color(ecbdata->color_diff,
-				       line[0] == '-' ? DIFF_FILE_OLD : DIFF_PLAIN);
-		ecbdata->lno_in_preimage++;
-		if (line[0] == ' ')
-			ecbdata->lno_in_postimage++;
-		emit_line(ecbdata->opt, color, reset, line, len);
-	} else {
+	switch (line[0]) {
+	case '+':
 		ecbdata->lno_in_postimage++;
 		emit_add_line(reset, ecbdata, line + 1, len - 1);
+		break;
+	case '-':
+		ecbdata->lno_in_preimage++;
+		emit_del_line(reset, ecbdata, line + 1, len - 1);
+		break;
+	case ' ':
+		ecbdata->lno_in_postimage++;
+		ecbdata->lno_in_preimage++;
+		emit_context_line(reset, ecbdata, line + 1, len - 1);
+		break;
+	default:
+		/* incomplete line at the end */
+		ecbdata->lno_in_preimage++;
+		emit_line(ecbdata->opt,
+			  diff_get_color(ecbdata->color_diff, DIFF_PLAIN),
+			  reset, line, len);
+		break;
 	}
 }
 
@@ -3223,6 +3264,7 @@ void diff_setup(struct diff_options *options)
 	options->rename_limit = -1;
 	options->dirstat_permille = diff_dirstat_permille_default;
 	options->context = diff_context_default;
+	options->ws_error_highlight = WSEH_NEW;
 	DIFF_OPT_SET(options, RENAME_EMPTY);
 
 	/* pathchange left =NULL by default */
@@ -3609,6 +3651,40 @@ static void enable_patch_output(int *fmt) {
 	*fmt |= DIFF_FORMAT_PATCH;
 }
 
+static int parse_one_token(const char **arg, const char *token)
+{
+	return skip_prefix(*arg, token, arg) && (!**arg || **arg == ',');
+}
+
+static int parse_ws_error_highlight(struct diff_options *opt, const char *arg)
+{
+	const char *orig_arg = arg;
+	unsigned val = 0;
+	while (*arg) {
+		if (parse_one_token(&arg, "none"))
+			val = 0;
+		else if (parse_one_token(&arg, "default"))
+			val = WSEH_NEW;
+		else if (parse_one_token(&arg, "all"))
+			val = WSEH_NEW | WSEH_OLD | WSEH_CONTEXT;
+		else if (parse_one_token(&arg, "new"))
+			val |= WSEH_NEW;
+		else if (parse_one_token(&arg, "old"))
+			val |= WSEH_OLD;
+		else if (parse_one_token(&arg, "context"))
+			val |= WSEH_CONTEXT;
+		else {
+			error("unknown value after ws-error-highlight=%.*s",
+			      (int)(arg - orig_arg), orig_arg);
+			return 0;
+		}
+		if (*arg)
+			arg++;
+	}
+	opt->ws_error_highlight = val;
+	return 1;
+}
+
 int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 {
 	const char *arg = av[0];
@@ -3806,6 +3882,8 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		DIFF_OPT_SET(options, SUBMODULE_LOG);
 	else if (skip_prefix(arg, "--submodule=", &arg))
 		return parse_submodule_opt(options, arg);
+	else if (skip_prefix(arg, "--ws-error-highlight=", &arg))
+		return parse_ws_error_highlight(options, arg);
 
 	/* misc options */
 	else if (!strcmp(arg, "-z"))
diff --git a/diff.h b/diff.h
index f6fdf49e14..57762ee8b1 100644
--- a/diff.h
+++ b/diff.h
@@ -138,6 +138,11 @@ struct diff_options {
 	int dirstat_permille;
 	int setup;
 	int abbrev;
+/* white-space error highlighting */
+#define WSEH_NEW 1
+#define WSEH_CONTEXT 2
+#define WSEH_OLD 4
+	unsigned ws_error_highlight;
 	const char *prefix;
 	int prefix_length;
 	const char *stat_sep;
diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index 604a838c1a..2434157aa7 100755
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -9,138 +9,144 @@ test_description='Test special whitespace in diff engine.
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/diff-lib.sh
 
-# Ray Lehtiniemi's example
+test_expect_success "Ray Lehtiniemi's example" '
+	cat <<-\EOF >x &&
+	do {
+	   nothing;
+	} while (0);
+	EOF
+	git update-index --add x &&
 
-cat << EOF > x
-do {
-   nothing;
-} while (0);
-EOF
+	cat <<-\EOF >x &&
+	do
+	{
+	   nothing;
+	}
+	while (0);
+	EOF
+
+	cat <<-\EOF >expect &&
+	diff --git a/x b/x
+	index adf3937..6edc172 100644
+	--- a/x
+	+++ b/x
+	@@ -1,3 +1,5 @@
+	-do {
+	+do
+	+{
+	    nothing;
+	-} while (0);
+	+}
+	+while (0);
+	EOF
 
-git update-index --add x
+	git diff >out &&
+	test_cmp expect out &&
 
-cat << EOF > x
-do
-{
-   nothing;
-}
-while (0);
-EOF
+	git diff -w >out &&
+	test_cmp expect out &&
 
-cat << EOF > expect
-diff --git a/x b/x
-index adf3937..6edc172 100644
---- a/x
-+++ b/x
-@@ -1,3 +1,5 @@
--do {
-+do
-+{
-    nothing;
--} while (0);
-+}
-+while (0);
-EOF
+	git diff -b >out &&
+	test_cmp expect out
+'
 
-git diff > out
-test_expect_success "Ray's example without options" 'test_cmp expect out'
+test_expect_success 'another test, without options' '
+	tr Q "\015" <<-\EOF >x &&
+	whitespace at beginning
+	whitespace change
+	whitespace in the middle
+	whitespace at end
+	unchanged line
+	CR at endQ
+	EOF
 
-git diff -w > out
-test_expect_success "Ray's example with -w" 'test_cmp expect out'
+	git update-index x &&
 
-git diff -b > out
-test_expect_success "Ray's example with -b" 'test_cmp expect out'
+	tr "_" " " <<-\EOF >x &&
+	_	whitespace at beginning
+	whitespace 	 change
+	white space in the middle
+	whitespace at end__
+	unchanged line
+	CR at end
+	EOF
 
-tr 'Q' '\015' << EOF > x
-whitespace at beginning
-whitespace change
-whitespace in the middle
-whitespace at end
-unchanged line
-CR at endQ
-EOF
+	tr "Q_" "\015 " <<-\EOF >expect &&
+	diff --git a/x b/x
+	index d99af23..22d9f73 100644
+	--- a/x
+	+++ b/x
+	@@ -1,6 +1,6 @@
+	-whitespace at beginning
+	-whitespace change
+	-whitespace in the middle
+	-whitespace at end
+	+ 	whitespace at beginning
+	+whitespace 	 change
+	+white space in the middle
+	+whitespace at end__
+	 unchanged line
+	-CR at endQ
+	+CR at end
+	EOF
 
-git update-index x
+	git diff >out &&
+	test_cmp expect out &&
 
-tr '_' ' ' << EOF > x
-	whitespace at beginning
-whitespace 	 change
-white space in the middle
-whitespace at end__
-unchanged line
-CR at end
-EOF
+	>expect &&
+	git diff -w >out &&
+	test_cmp expect out &&
 
-tr 'Q_' '\015 ' << EOF > expect
-diff --git a/x b/x
-index d99af23..8b32fb5 100644
---- a/x
-+++ b/x
-@@ -1,6 +1,6 @@
--whitespace at beginning
--whitespace change
--whitespace in the middle
--whitespace at end
-+	whitespace at beginning
-+whitespace 	 change
-+white space in the middle
-+whitespace at end__
- unchanged line
--CR at endQ
-+CR at end
-EOF
-git diff > out
-test_expect_success 'another test, without options' 'test_cmp expect out'
+	git diff -w -b >out &&
+	test_cmp expect out &&
 
-cat << EOF > expect
-EOF
-git diff -w > out
-test_expect_success 'another test, with -w' 'test_cmp expect out'
-git diff -w -b > out
-test_expect_success 'another test, with -w -b' 'test_cmp expect out'
-git diff -w --ignore-space-at-eol > out
-test_expect_success 'another test, with -w --ignore-space-at-eol' 'test_cmp expect out'
-git diff -w -b --ignore-space-at-eol > out
-test_expect_success 'another test, with -w -b --ignore-space-at-eol' 'test_cmp expect out'
-
-tr 'Q_' '\015 ' << EOF > expect
-diff --git a/x b/x
-index d99af23..8b32fb5 100644
---- a/x
-+++ b/x
-@@ -1,6 +1,6 @@
--whitespace at beginning
-+	whitespace at beginning
- whitespace 	 change
--whitespace in the middle
-+white space in the middle
- whitespace at end__
- unchanged line
- CR at end
-EOF
-git diff -b > out
-test_expect_success 'another test, with -b' 'test_cmp expect out'
-git diff -b --ignore-space-at-eol > out
-test_expect_success 'another test, with -b --ignore-space-at-eol' 'test_cmp expect out'
-
-tr 'Q_' '\015 ' << EOF > expect
-diff --git a/x b/x
-index d99af23..8b32fb5 100644
---- a/x
-+++ b/x
-@@ -1,6 +1,6 @@
--whitespace at beginning
--whitespace change
--whitespace in the middle
-+	whitespace at beginning
-+whitespace 	 change
-+white space in the middle
- whitespace at end__
- unchanged line
- CR at end
-EOF
-git diff --ignore-space-at-eol > out
-test_expect_success 'another test, with --ignore-space-at-eol' 'test_cmp expect out'
+	git diff -w --ignore-space-at-eol >out &&
+	test_cmp expect out &&
+
+	git diff -w -b --ignore-space-at-eol >out &&
+	test_cmp expect out &&
+
+
+	tr "Q_" "\015 " <<-\EOF >expect &&
+	diff --git a/x b/x
+	index d99af23..22d9f73 100644
+	--- a/x
+	+++ b/x
+	@@ -1,6 +1,6 @@
+	-whitespace at beginning
+	+_	whitespace at beginning
+	 whitespace 	 change
+	-whitespace in the middle
+	+white space in the middle
+	 whitespace at end__
+	 unchanged line
+	 CR at end
+	EOF
+	git diff -b >out &&
+	test_cmp expect out &&
+
+	git diff -b --ignore-space-at-eol >out &&
+	test_cmp expect out &&
+
+	tr "Q_" "\015 " <<-\EOF >expect &&
+	diff --git a/x b/x
+	index d99af23..22d9f73 100644
+	--- a/x
+	+++ b/x
+	@@ -1,6 +1,6 @@
+	-whitespace at beginning
+	-whitespace change
+	-whitespace in the middle
+	+_	whitespace at beginning
+	+whitespace 	 change
+	+white space in the middle
+	 whitespace at end__
+	 unchanged line
+	 CR at end
+	EOF
+	git diff --ignore-space-at-eol >out &&
+	test_cmp expect out
+'
 
 test_expect_success 'ignore-blank-lines: only new lines' '
 	test_seq 5 >x &&
@@ -489,291 +495,219 @@ test_expect_success 'ignore-blank-lines: mix changes and blank lines' '
 '
 
 test_expect_success 'check mixed spaces and tabs in indent' '
-
 	# This is indented with SP HT SP.
-	echo " 	 foo();" > x &&
+	echo " 	 foo();" >x &&
 	git diff --check | grep "space before tab in indent"
-
 '
 
 test_expect_success 'check mixed tabs and spaces in indent' '
-
 	# This is indented with HT SP HT.
-	echo "	 	foo();" > x &&
+	echo "	 	foo();" >x &&
 	git diff --check | grep "space before tab in indent"
-
 '
 
 test_expect_success 'check with no whitespace errors' '
-
 	git commit -m "snapshot" &&
-	echo "foo();" > x &&
+	echo "foo();" >x &&
 	git diff --check
-
 '
 
 test_expect_success 'check with trailing whitespace' '
-
-	echo "foo(); " > x &&
+	echo "foo(); " >x &&
 	test_must_fail git diff --check
-
 '
 
 test_expect_success 'check with space before tab in indent' '
-
 	# indent has space followed by hard tab
-	echo " 	foo();" > x &&
+	echo " 	foo();" >x &&
 	test_must_fail git diff --check
-
 '
 
 test_expect_success '--check and --exit-code are not exclusive' '
-
 	git checkout x &&
 	git diff --check --exit-code
-
 '
 
 test_expect_success '--check and --quiet are not exclusive' '
-
 	git diff --check --quiet
-
 '
 
 test_expect_success 'check staged with no whitespace errors' '
-
-	echo "foo();" > x &&
+	echo "foo();" >x &&
 	git add x &&
 	git diff --cached --check
-
 '
 
 test_expect_success 'check staged with trailing whitespace' '
-
-	echo "foo(); " > x &&
+	echo "foo(); " >x &&
 	git add x &&
 	test_must_fail git diff --cached --check
-
 '
 
 test_expect_success 'check staged with space before tab in indent' '
-
 	# indent has space followed by hard tab
-	echo " 	foo();" > x &&
+	echo " 	foo();" >x &&
 	git add x &&
 	test_must_fail git diff --cached --check
-
 '
 
 test_expect_success 'check with no whitespace errors (diff-index)' '
-
-	echo "foo();" > x &&
+	echo "foo();" >x &&
 	git add x &&
 	git diff-index --check HEAD
-
 '
 
 test_expect_success 'check with trailing whitespace (diff-index)' '
-
-	echo "foo(); " > x &&
+	echo "foo(); " >x &&
 	git add x &&
 	test_must_fail git diff-index --check HEAD
-
 '
 
 test_expect_success 'check with space before tab in indent (diff-index)' '
-
 	# indent has space followed by hard tab
-	echo " 	foo();" > x &&
+	echo " 	foo();" >x &&
 	git add x &&
 	test_must_fail git diff-index --check HEAD
-
 '
 
 test_expect_success 'check staged with no whitespace errors (diff-index)' '
-
-	echo "foo();" > x &&
+	echo "foo();" >x &&
 	git add x &&
 	git diff-index --cached --check HEAD
-
 '
 
 test_expect_success 'check staged with trailing whitespace (diff-index)' '
-
-	echo "foo(); " > x &&
+	echo "foo(); " >x &&
 	git add x &&
 	test_must_fail git diff-index --cached --check HEAD
-
 '
 
 test_expect_success 'check staged with space before tab in indent (diff-index)' '
-
 	# indent has space followed by hard tab
-	echo " 	foo();" > x &&
+	echo " 	foo();" >x &&
 	git add x &&
 	test_must_fail git diff-index --cached --check HEAD
-
 '
 
 test_expect_success 'check with no whitespace errors (diff-tree)' '
-
-	echo "foo();" > x &&
+	echo "foo();" >x &&
 	git commit -m "new commit" x &&
 	git diff-tree --check HEAD^ HEAD
-
 '
 
 test_expect_success 'check with trailing whitespace (diff-tree)' '
-
-	echo "foo(); " > x &&
+	echo "foo(); " >x &&
 	git commit -m "another commit" x &&
 	test_must_fail git diff-tree --check HEAD^ HEAD
-
 '
 
 test_expect_success 'check with space before tab in indent (diff-tree)' '
-
 	# indent has space followed by hard tab
-	echo " 	foo();" > x &&
+	echo " 	foo();" >x &&
 	git commit -m "yet another" x &&
 	test_must_fail git diff-tree --check HEAD^ HEAD
-
 '
 
 test_expect_success 'check trailing whitespace (trailing-space: off)' '
-
 	git config core.whitespace "-trailing-space" &&
-	echo "foo ();   " > x &&
+	echo "foo ();   " >x &&
 	git diff --check
-
 '
 
 test_expect_success 'check trailing whitespace (trailing-space: on)' '
-
 	git config core.whitespace "trailing-space" &&
-	echo "foo ();   " > x &&
+	echo "foo ();   " >x &&
 	test_must_fail git diff --check
-
 '
 
 test_expect_success 'check space before tab in indent (space-before-tab: off)' '
-
 	# indent contains space followed by HT
 	git config core.whitespace "-space-before-tab" &&
-	echo " 	foo ();" > x &&
+	echo " 	foo ();" >x &&
 	git diff --check
-
 '
 
 test_expect_success 'check space before tab in indent (space-before-tab: on)' '
-
 	# indent contains space followed by HT
 	git config core.whitespace "space-before-tab" &&
-	echo " 	foo ();   " > x &&
+	echo " 	foo ();   " >x &&
 	test_must_fail git diff --check
-
 '
 
 test_expect_success 'check spaces as indentation (indent-with-non-tab: off)' '
-
 	git config core.whitespace "-indent-with-non-tab" &&
-	echo "        foo ();" > x &&
+	echo "        foo ();" >x &&
 	git diff --check
-
 '
 
 test_expect_success 'check spaces as indentation (indent-with-non-tab: on)' '
-
 	git config core.whitespace "indent-with-non-tab" &&
-	echo "        foo ();" > x &&
+	echo "        foo ();" >x &&
 	test_must_fail git diff --check
-
 '
 
 test_expect_success 'ditto, but tabwidth=9' '
-
 	git config core.whitespace "indent-with-non-tab,tabwidth=9" &&
 	git diff --check
-
 '
 
 test_expect_success 'check tabs and spaces as indentation (indent-with-non-tab: on)' '
-
 	git config core.whitespace "indent-with-non-tab" &&
-	echo "	                foo ();" > x &&
+	echo "	                foo ();" >x &&
 	test_must_fail git diff --check
-
 '
 
 test_expect_success 'ditto, but tabwidth=10' '
-
 	git config core.whitespace "indent-with-non-tab,tabwidth=10" &&
 	test_must_fail git diff --check
-
 '
 
 test_expect_success 'ditto, but tabwidth=20' '
-
 	git config core.whitespace "indent-with-non-tab,tabwidth=20" &&
 	git diff --check
-
 '
 
 test_expect_success 'check tabs as indentation (tab-in-indent: off)' '
-
 	git config core.whitespace "-tab-in-indent" &&
-	echo "	foo ();" > x &&
+	echo "	foo ();" >x &&
 	git diff --check
-
 '
 
 test_expect_success 'check tabs as indentation (tab-in-indent: on)' '
-
 	git config core.whitespace "tab-in-indent" &&
-	echo "	foo ();" > x &&
+	echo "	foo ();" >x &&
 	test_must_fail git diff --check
-
 '
 
 test_expect_success 'check tabs and spaces as indentation (tab-in-indent: on)' '
-
 	git config core.whitespace "tab-in-indent" &&
-	echo "	                foo ();" > x &&
+	echo "	                foo ();" >x &&
 	test_must_fail git diff --check
-
 '
 
 test_expect_success 'ditto, but tabwidth=1 (must be irrelevant)' '
-
 	git config core.whitespace "tab-in-indent,tabwidth=1" &&
 	test_must_fail git diff --check
-
 '
 
 test_expect_success 'check tab-in-indent and indent-with-non-tab conflict' '
-
 	git config core.whitespace "tab-in-indent,indent-with-non-tab" &&
-	echo "foo ();" > x &&
+	echo "foo ();" >x &&
 	test_must_fail git diff --check
-
 '
 
 test_expect_success 'check tab-in-indent excluded from wildcard whitespace attribute' '
-
 	git config --unset core.whitespace &&
-	echo "x whitespace" > .gitattributes &&
-	echo "	  foo ();" > x &&
+	echo "x whitespace" >.gitattributes &&
+	echo "	  foo ();" >x &&
 	git diff --check &&
 	rm -f .gitattributes
-
 '
 
 test_expect_success 'line numbers in --check output are correct' '
-
-	echo "" > x &&
-	echo "foo(); " >> x &&
+	echo "" >x &&
+	echo "foo(); " >>x &&
 	git diff --check | grep "x:2:"
-
 '
 
 test_expect_success 'checkdiff detects new trailing blank lines (1)' '
@@ -876,29 +810,127 @@ test_expect_success 'setup diff colors' '
 	git config color.diff.old red &&
 	git config color.diff.new green &&
 	git config color.diff.commit yellow &&
-	git config color.diff.whitespace "normal red" &&
+	git config color.diff.whitespace blue &&
 
 	git config core.autocrlf false
 '
-cat >expected <<\EOF
-<BOLD>diff --git a/x b/x<RESET>
-<BOLD>index 9daeafb..2874b91 100644<RESET>
-<BOLD>--- a/x<RESET>
-<BOLD>+++ b/x<RESET>
-<CYAN>@@ -1 +1,4 @@<RESET>
- test<RESET>
-<GREEN>+<RESET><GREEN>{<RESET>
-<GREEN>+<RESET><BRED>	<RESET>
-<GREEN>+<RESET><GREEN>}<RESET>
-EOF
 
 test_expect_success 'diff that introduces a line with only tabs' '
 	git config core.whitespace blank-at-eol &&
 	git reset --hard &&
-	echo "test" > x &&
+	echo "test" >x &&
 	git commit -m "initial" x &&
-	echo "{NTN}" | tr "NT" "\n\t" >> x &&
+	echo "{NTN}" | tr "NT" "\n\t" >>x &&
 	git -c color.diff=always diff | test_decode_color >current &&
+
+	cat >expected <<-\EOF &&
+	<BOLD>diff --git a/x b/x<RESET>
+	<BOLD>index 9daeafb..2874b91 100644<RESET>
+	<BOLD>--- a/x<RESET>
+	<BOLD>+++ b/x<RESET>
+	<CYAN>@@ -1 +1,4 @@<RESET>
+	 test<RESET>
+	<GREEN>+<RESET><GREEN>{<RESET>
+	<GREEN>+<RESET><BLUE>	<RESET>
+	<GREEN>+<RESET><GREEN>}<RESET>
+	EOF
+
+	test_cmp expected current
+'
+
+test_expect_success 'diff that introduces and removes ws breakages' '
+	git reset --hard &&
+	{
+		echo "0. blank-at-eol " &&
+		echo "1. blank-at-eol "
+	} >x &&
+	git commit -a --allow-empty -m preimage &&
+	{
+		echo "0. blank-at-eol " &&
+		echo "1. still-blank-at-eol " &&
+		echo "2. and a new line "
+	} >x &&
+
+	git -c color.diff=always diff |
+	test_decode_color >current &&
+
+	cat >expected <<-\EOF &&
+	<BOLD>diff --git a/x b/x<RESET>
+	<BOLD>index d0233a2..700886e 100644<RESET>
+	<BOLD>--- a/x<RESET>
+	<BOLD>+++ b/x<RESET>
+	<CYAN>@@ -1,2 +1,3 @@<RESET>
+	 0. blank-at-eol <RESET>
+	<RED>-1. blank-at-eol <RESET>
+	<GREEN>+<RESET><GREEN>1. still-blank-at-eol<RESET><BLUE> <RESET>
+	<GREEN>+<RESET><GREEN>2. and a new line<RESET><BLUE> <RESET>
+	EOF
+
+	test_cmp expected current
+'
+
+test_expect_success 'the same with --ws-error-highlight' '
+	git reset --hard &&
+	{
+		echo "0. blank-at-eol " &&
+		echo "1. blank-at-eol "
+	} >x &&
+	git commit -a --allow-empty -m preimage &&
+	{
+		echo "0. blank-at-eol " &&
+		echo "1. still-blank-at-eol " &&
+		echo "2. and a new line "
+	} >x &&
+
+	git -c color.diff=always diff --ws-error-highlight=default,old |
+	test_decode_color >current &&
+
+	cat >expected <<-\EOF &&
+	<BOLD>diff --git a/x b/x<RESET>
+	<BOLD>index d0233a2..700886e 100644<RESET>
+	<BOLD>--- a/x<RESET>
+	<BOLD>+++ b/x<RESET>
+	<CYAN>@@ -1,2 +1,3 @@<RESET>
+	 0. blank-at-eol <RESET>
+	<RED>-<RESET><RED>1. blank-at-eol<RESET><BLUE> <RESET>
+	<GREEN>+<RESET><GREEN>1. still-blank-at-eol<RESET><BLUE> <RESET>
+	<GREEN>+<RESET><GREEN>2. and a new line<RESET><BLUE> <RESET>
+	EOF
+
+	test_cmp expected current &&
+
+	git -c color.diff=always diff --ws-error-highlight=all |
+	test_decode_color >current &&
+
+	cat >expected <<-\EOF &&
+	<BOLD>diff --git a/x b/x<RESET>
+	<BOLD>index d0233a2..700886e 100644<RESET>
+	<BOLD>--- a/x<RESET>
+	<BOLD>+++ b/x<RESET>
+	<CYAN>@@ -1,2 +1,3 @@<RESET>
+	 <RESET>0. blank-at-eol<RESET><BLUE> <RESET>
+	<RED>-<RESET><RED>1. blank-at-eol<RESET><BLUE> <RESET>
+	<GREEN>+<RESET><GREEN>1. still-blank-at-eol<RESET><BLUE> <RESET>
+	<GREEN>+<RESET><GREEN>2. and a new line<RESET><BLUE> <RESET>
+	EOF
+
+	test_cmp expected current &&
+
+	git -c color.diff=always diff --ws-error-highlight=none |
+	test_decode_color >current &&
+
+	cat >expected <<-\EOF &&
+	<BOLD>diff --git a/x b/x<RESET>
+	<BOLD>index d0233a2..700886e 100644<RESET>
+	<BOLD>--- a/x<RESET>
+	<BOLD>+++ b/x<RESET>
+	<CYAN>@@ -1,2 +1,3 @@<RESET>
+	 0. blank-at-eol <RESET>
+	<RED>-1. blank-at-eol <RESET>
+	<GREEN>+1. still-blank-at-eol <RESET>
+	<GREEN>+2. and a new line <RESET>
+	EOF
+
 	test_cmp expected current
 '