Code review comment for lp:~parthm/bzr/138600

The NEWS entry is a bit unclear. Perhaps:

* ``bzr mkdir DIR`` will not create DIR unless DIR's parent is a versioned directory. (Parth Malwankar, #138600)

(with appropriate word-wrapping, of course).

The tests look like they cover all the interesting cases, thanks! They are a bit oddly inconsistent cosmetically (e.g. calling run_bzr with 'mkdir abc' vs. ['mkdir', 'abc']), but that's not a big deal.