man 1p printf:
   In addition to the escape sequences shown in the Base Definitions
   volume of POSIX.1‐2008, Chapter 5, File Format Notation ('\\',
   '\a', '\b', '\f', '\n', '\r', '\t', '\v'), "\ddd", where ddd is a
   one, two, or three-digit octal number, shall be written as a byte
   with the numeric value specified by the octal number.

printf '\xfe\xff' in an extension of some libc.

With dash:
$ printf '\xfe\xff' | xxd
00000000: 5c78 6665 5c78 6666                      \xfe\xff

Correct its usage.

Signed-off-by: Doan Tran Cong Danh <redacted>
---

Notes:
    Despite that dash's printf doesn't accept \x escape sequence.
    
    My glibc box (with sh linked to dash) can run the test just fine.
    But my musl box couldn't run the test, (because the header).

 t/t0028-working-tree-encoding.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/t/t0028-working-tree-encoding.sh b/t/t0028-working-tree-encoding.sh
index 7aa0945d8d..bfc4fb9af5 100755
--- a/t/t0028-working-tree-encoding.sh
+++ b/t/t0028-working-tree-encoding.sh

@@ -17,7 +17,7 @@ test_lazy_prereq NO_UTF32_BOM '
 write_utf16 () {
 	if test_have_prereq NO_UTF16_BOM
 	then
-		printf '\xfe\xff'
+		printf '\376\377'
 	fi &&
 	iconv -f UTF-8 -t UTF-16
 }

@@ -25,7 +25,7 @@ write_utf16 () {
 write_utf32 () {
 	if test_have_prereq NO_UTF32_BOM
 	then
-		printf '\x00\x00\xfe\xff'
+		printf '\0\0\376\377'
 	fi &&
 	iconv -f UTF-8 -t UTF-32
 }

-- 
2.24.0.rc1.3.g89530838a3.dirty