diff: do not chomp hunk-header in the middle of a character

We truncate hunk-header line at 80 bytes, but that 80th byte
could be in the middle of a character, which is bad.  This uses
pick_one_utf8_char() function to make sure we do not cut a character
in the middle.

This assumes that the internal representation of the text is
UTF-8.  This needs to be extended in the future but the optimal
direction has not been decided yet.

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

1 files changed, 44 insertions, 0 deletions

diff --git a/t/t4025-hunk-header.sh b/t/t4025-hunk-header.sh
new file mode 100755
index 0000000000..9ba06b74ce
--- /dev/null
+++ b/t/t4025-hunk-header.sh
@@ -0,0 +1,44 @@
+#!/bin/sh
+
+test_description='diff hunk header truncation'
+
+. ./test-lib.sh
+
+N='日本語'
+N1='日'
+N2='日本'
+NS="$N$N$N$N$N$N$N$N$N$N$N$N$N"
+
+test_expect_success setup '
+
+	(
+		echo "A $NS"
+		for c in B C D E F G H I J K
+		do
+			echo "  $c"
+		done
+		echo "L  $NS"
+		for c in M N O P Q R S T U V
+		do
+			echo "  $c"
+		done
+	) >file &&
+	git add file &&
+
+	sed -e "/^  [EP]/s/$/ modified/" <file >file+ &&
+	mv file+ file
+
+'
+
+test_expect_success 'hunk header truncation with an overly long line' '
+
+	git diff | sed -n -e "s/^.*@@//p" >actual &&
+	(
+		echo " A $N$N$N$N$N$N$N$N$N2"
+		echo " L  $N$N$N$N$N$N$N$N$N1"
+	) >expected &&
+	diff -u actual expected
+
+'
+
+test_done