[Proposed Fix v1] t5318: replace dd if=/dev/zero with truncate

[randall.s.becker@rogers.com]

From: "Randall S. Becker" <rsbecker@nexbridge.com>

The corrupt_graph_and_verify method has been modified to use
truncate instead of the /dev/zero pseudo-device, which breaks on
platforms where the pseudo-device does not exist. truncate extends
files to a specified length filling with nulls, providing a similar
function to the use of dd in this case.

Signed-off-by: Randall S. Becker <rsbecker@nexbridge.com>
---
 t/t5318-commit-graph.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index 16d10ebce..d627ffe09 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -383,7 +383,7 @@ corrupt_graph_and_verify() {
 	cp $objdir/info/commit-graph commit-graph-backup &&
 	printf "$data" | dd of="$objdir/info/commit-graph" bs=1 seek="$pos" conv=notrunc &&
 	dd of="$objdir/info/commit-graph" bs=1 seek="$zero_pos" count=0 &&
-	dd if=/dev/zero of="$objdir/info/commit-graph" bs=1 seek="$zero_pos" count=$(($orig_size - $zero_pos)) &&
+	truncate -s $orig_size "$objdir/info/commit-graph" &&
 	test_must_fail git commit-graph verify 2>test_err &&
 	grep -v "^+" test_err >err &&
 	test_i18ngrep "$grepstr" err
-- 
2.12.3