message: Make unlink behaviour explicit
diff: @@ -437,16 +437,22 @@ pub mod tests {
  with_tmp_dir(|dir| {
  let file1 = dir.join("foo.h5");
  let file1 = File::create(file1).unwrap();
  - let dset = file1.new_dataset::<i32>().create("foo").unwrap();
  - dset.write_scalar(&13).unwrap();
  + let dset1 = file1.new_dataset::<i32>().create("foo").unwrap();
  + dset1.write_scalar(&13).unwrap();
  let file2 = dir.join("bar.h5");
  let file2 = File::create(file2).unwrap();
  file2.link_external("foo.h5", "foo", "bar").unwrap();
  - assert_eq!(file2.dataset("bar").unwrap().read_scalar::<i32>().unwrap(), 13);
  + let dset2 = file2.dataset("bar").unwrap();
  + assert_eq!(dset2.read_scalar::<i32>().unwrap(), 13);
  file1.unlink("foo").unwrap();
  + assert!(file1.dataset("foo").is_err());
  assert!(file2.dataset("bar").is_err());
  +
  + // foo is only weakly closed
  + assert_eq!(dset1.read_scalar::<i32>().unwrap(), 13);
  + assert_eq!(dset2.read_scalar::<i32>().unwrap(), 13);
  })
  }
  }
  