Use .git::$INDEX_ALLOCATION instead of .git:$I30

This seems more effective at revealing such a vulnerability.

I don't know why, since both should in principle work fine.

Author: EliahKagan

gix-worktree/tests/fixtures/make_traverse_ntfs_stream.sh

@@ -6,7 +6,7 @@ git init -- "$repo"
 cd -- "$repo"
 
 # shellcheck disable=SC2016
-target_dir='subdir/.git:$I30/hooks'
+target_dir='subdir/.git::$INDEX_ALLOCATION/hooks'
 target_dir_standin="$(printf '%s' "$target_dir" | sed 's|:|,|g')"
 target_file="$target_dir/pre-commit"
 target_file_standin="$target_dir_standin/pre-commit"