t9300: factor out portable "head -c" replacement

diff --git a/t/t6041-bisect-submodule.sh b/t/t6041-bisect-submodule.sh
index c6b7aa6977e0a5a1017c759d93f8883cad3713b0..62b8a2e7bbd1cf26710be0a0eb90041d5e3f7d2c 100755 (executable)
--- a/t/t6041-bisect-submodule.sh
+++ b/t/t6041-bisect-submodule.sh
@@ -8,7 +8,7 @@ test_description='bisect can handle submodules'
 git_bisect () {
        git status -su >expect &&
        ls -1pR * >>expect &&
-       tar czf "$TRASH_DIRECTORY/tmp.tgz" * &&
+       tar cf "$TRASH_DIRECTORY/tmp.tar" * &&
        GOOD=$(git rev-parse --verify HEAD) &&
        git checkout "$1" &&
        echo "foo" >bar &&
@@ -20,7 +20,7 @@ git_bisect () {
        git bisect start &&
        git bisect good $GOOD &&
        rm -rf * &&
-       tar xzf "$TRASH_DIRECTORY/tmp.tgz" &&
+       tar xf "$TRASH_DIRECTORY/tmp.tar" &&
        git status -su >actual &&
        ls -1pR * >>actual &&
        test_cmp expect actual &&