code: private Lease lease(@Nonnull FilePath p) {
          return new Lease(p) {
              final AtomicBoolean released = new AtomicBoolean();
              public void release() {
                  _release(path);
              }
              @Override public void close() {
                  if (released.compareAndSet(false, true)) {
                      release();
                  }
              }
          };
      }
docs: Wraps a path into a valid lease.