commit: reject non-characters

Unicode clause D14 defines all characters U+nFFFE and U+nFFFF (where
0 <= n <= 10h) as well as the range U+FDD0..U+FDEF as non-characters,
reserved for internal use only.  Disallow these characters in commit
messages as they are normally not recommended for interchange.

Signed-off-by: Peter Krefting <peter@softwolves.pp.se>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

commit.c

@@ -1305,8 +1305,11 @@ static int find_invalid_utf8(const char *buf, int len)
 		/* Surrogates are only for UTF-16 and cannot be encoded in UTF-8. */
 		if ((codepoint & 0x1ff800) == 0xd800)
 			return bad_offset;
-		/* U+FFFE and U+FFFF are guaranteed non-characters. */
-		if ((codepoint & 0x1ffffe) == 0xfffe)
+		/* U+xxFFFE and U+xxFFFF are guaranteed non-characters. */
+		if ((codepoint & 0xffffe) == 0xfffe)
+			return bad_offset;
+		/* So are anything in the range U+FDD0..U+FDEF. */
+		if (codepoint >= 0xfdd0 && codepoint <= 0xfdef)
 			return bad_offset;
 	}
 	return -1;

t/t3900-i18n-commit.sh

@@ -58,6 +58,24 @@ test_expect_success 'UTF-8 overlong sequences rejected' '
 	grep "did not conform" "$HOME"/stderr
 '
 
+test_expect_success 'UTF-8 non-characters refused' '
+	test_when_finished "rm -f $HOME/stderr $HOME/invalid" &&
+	echo "UTF-8 non-character 1" >F &&
+	printf "Commit message\n\nNon-character:\364\217\277\276\n" \
+		>"$HOME/invalid" &&
+	git commit -a -F "$HOME/invalid" 2>"$HOME"/stderr &&
+	grep "did not conform" "$HOME"/stderr
+'
+
+test_expect_success 'UTF-8 non-characters refused' '
+	test_when_finished "rm -f $HOME/stderr $HOME/invalid" &&
+	echo "UTF-8 non-character 2." >F &&
+	printf "Commit message\n\nNon-character:\357\267\220\n" \
+		>"$HOME/invalid" &&
+	git commit -a -F "$HOME/invalid" 2>"$HOME"/stderr &&
+	grep "did not conform" "$HOME"/stderr
+'
+
 for H in ISO8859-1 eucJP ISO-2022-JP
 do
 	test_expect_success "$H setup" '