midx: predict packfile name size using wc

Signed-off-by: Derrick Stolee <[email protected]>

Author: derrickstolee

t/t5319-midx.sh

@@ -262,8 +262,8 @@ MIDX_BYTE_OBJECT_OFFSET=`expr $MIDX_OFFSET_OBJECT_OFFSETS + \
 MIDX_OFFSET_PACKFILE_NAMES=`expr $MIDX_OFFSET_OBJECT_OFFSETS + \
 				$MIDX_WIDTH_OBJECT_OFFSETS \* $MIDX_NUM_OBJECTS`
 MIDX_BYTE_PACKFILE_NAMES=`expr $MIDX_OFFSET_PACKFILE_NAMES + 10`
-MIDX_LEN=$(stat --printf="%s" midx-*.midx)
-MIDX_BYTE_CHECKSUM=`expr $MIDX_LEN - $HASH_LEN`
+MIDX_PACKNAME_SIZE=`expr $(ls *.pack | wc -c) + $MIDX_NUM_PACKS`
+MIDX_BYTE_CHECKSUM=`expr $MIDX_OFFSET_PACKFILE_NAMES + $MIDX_PACKNAME_SIZE`
 
 test_expect_success 'midx --verify succeeds' '
 	git midx --verify --pack-dir .