DirectoryEntry lookUp(File workingDirectory, JimfsPath path, Set<? super LinkOption> options)
      throws IOException {
    state.checkOpen();
    return tree.lookUp(workingDirectory, path, options);
  }
Looks up the file at the given path using the given link options. If the path is relative, the
lookup is relative to the given working directory.

@throws NoSuchFileException if an element of the path other than the final element does not
    resolve to a directory or symbolic link (e.g. it doesn't exist or is a regular file)
@throws IOException if a symbolic link cycle is detected or the depth of symbolic link
    recursion otherwise exceeds a threshold
jimfs/src/main/java/com/google/common/jimfs/JimfsFileStore.java