diff.c: --ws-error-highlight=<kind> 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, those breakages are there but they
were inherited from the original, so let's not touch them for now."

Introduce `--ws-error-highlight=<kind>` option, that lets them pass
a comma separated list of `old`, `new`, and `context` to specify
what lines to highlight whitespace errors on.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 96 insertions, 0 deletions

diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index 4da30e5a1..2434157aa 100755
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -838,4 +838,100 @@ test_expect_success 'diff that introduces a line with only tabs' '
 	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
+'
+
 test_done