Close all opened dulwich repo objects
Close all opened dulwich repo objects

Otherwise, especially on Windows, we might end up with locked files.

Fix #138.

dulwich's pull can operate either on paths or on dulwich repo objects.
Since it's using `open_repo_closing` internally, if it (and hence
`open_repo_closing`) are passed a path, the associated repo object
will be automatically closed after use, so we don't have to worry
about anything.  (If they're passed an already existing "repo object",
as we had been doing previously, then, internally, they use
`_noop_context_manager()`, instead of `closing()` and the repo object
isn't closed.)

(The above is true for current dulwich master
(`80bffaca1dfe59a5ba57a045f3ce7122227a7647`) — see
`dulwich/porcelain.py`.)

Stvad/CrowdAnki,Stvad/CrowdAnki,Stvad/CrowdAnki