public void unlink(Name name) {
    DirectoryEntry entry = remove(checkNotReserved(name, "unlink"));
    entry.file().unlinked();
  }
Unlinks the given name from the file it is linked to.

@throws IllegalArgumentException if {@code name} is a reserved name such as "." or no entry
    exists for the name
jimfs/src/main/java/com/google/common/jimfs/Directory.java