t1050: match object ID paths in a hash-insensitive way

The pattern here looking for failures is specific to SHA-1.  Let's
create a variable that matches the regex or glob pattern for a path
within the objects directory.

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

t/t1050-large.sh

@@ -64,7 +64,7 @@ test_expect_success 'add a large file or two' '
 	test $count = 1 &&
 	cnt=$(git show-index <"$idx" | wc -l) &&
 	test $cnt = 2 &&
-	for l in .git/objects/??/??????????????????????????????????????
+	for l in .git/objects/$OIDPATH_REGEX
 	do
 		test_path_is_file "$l" || continue
 		bad=t

t/test-lib.sh

@@ -1428,6 +1428,7 @@ test_oid_init
 
 ZERO_OID=$(test_oid zero)
 OID_REGEX=$(echo $ZERO_OID | sed -e 's/0/[0-9a-f]/g')
+OIDPATH_REGEX=$(test_oid_to_path $ZERO_OID | sed -e 's/0/[0-9a-f]/g')
 EMPTY_TREE=$(test_oid empty_tree)
 EMPTY_BLOB=$(test_oid empty_blob)
 _z40=$ZERO_OID