t4134: compute appropriate length constant

Instead of using a specific invalid hard-coded object ID, generate one
of the appropriate length by looking one up in the translation tables.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4134-apply-submodule.sh

@@ -8,6 +8,7 @@ test_description='git apply submodule tests'
 . ./test-lib.sh
 
 test_expect_success setup '
+	test_oid_init &&
 	cat > create-sm.patch <<EOF &&
 diff --git a/dir/sm b/dir/sm
 new file mode 160000
@@ -15,7 +16,7 @@ index 0000000..0123456
 --- /dev/null
 +++ b/dir/sm
 @@ -0,0 +1 @@
-+Subproject commit 0123456789abcdef0123456789abcdef01234567
++Subproject commit $(test_oid numeric)
 EOF
 	cat > remove-sm.patch <<EOF
 diff --git a/dir/sm b/dir/sm
@@ -24,7 +25,7 @@ index 0123456..0000000
 --- a/dir/sm
 +++ /dev/null
 @@ -1 +0,0 @@
--Subproject commit 0123456789abcdef0123456789abcdef01234567
+-Subproject commit $(test_oid numeric)
 EOF
 '