py-dulwich: update to 0.20.15

0.20.15 2020-12-23

* Add some functions for parsing and writing bundles.
  (Jelmer Vernooij)

* Add ``no_verify`` flag to ``porcelain.commit`` and ``Repo.do_commit``.
  (Peter Rowlands)

* Remove dependency on external mock module.
  (Matěj Cepl, #820)

0.20.14 2020-11-26

* Fix some stash functions on Python 3. (Peter Rowlands)

* Fix handling of relative paths in alternates files on Python 3.
  (Georges Racinet)

0.20.13 2020-11-22

* Add py.typed to allow type checking. (David Caro)

* Add tests demonstrating a bug in the walker code.
  (Doug Hellman)

0.20.11 2020-10-30

* Fix wheels build on Linux. (Ruslan Kuprieiev)

* Enable wheels build for Python 3.9 on Linux. (Jelmer Vernooij)

0.20.8 2020-10-29

* Build wheels on Mac OS X / Windows for Python 3.9.
  (Jelmer Vernooij)

0.20.7 2020-10-29

* Check core.repositoryformatversion. (Jelmer Vernooij, #803)

* Fix ACK/NACK handling in archive command handling in dulwich.client.
  (DzmitrySudnik, #805)

0.20.6 2020-08-29

* Add a ``RefsContainer.watch`` interface.
  (Jelmer Vernooij, #751)

* Fix pushing of new branches from porcelain.push.
  (Jelmer Vernooij, #788)

* Honor shallows when pushing from a shallow clone.
  (Jelmer Vernooij, #794)

* Fix porcelain.path_to_tree_path for Python 3.5.
  (Boris Feld, #777)

* Add support for honor proxy environment variables for HTTP.
  (Aurélien Campéas, #797)

0.20.5 2020-06-22

* Print a clearer exception when setup.py is executed on Python < 3.5.
  (Jelmer Vernooij, #783)

* Send an empty pack to clients if they requested objects, even if they
  already have those objects. Thanks to Martijn Pieters for
  the detailed bug report. (Jelmer Vernooij, #781)

* porcelain.pull: Don't ask for objects that we already have.
  (Jelmer Vernooij, #782)

* Add LCA implementation. (Kevin Hendricks)

* Add functionality for finding the merge base. (Kevin Hendricks)

* Check for diverged branches during push.
  (Jelmer Vernooij, #494)

* Check for fast-forward during pull. (Jelmer Vernooij, #666)

* Return a SendPackResult object from
  GitClient.send_pack(). (Jelmer Vernooij)

* ``GitClient.send_pack`` now sets the ``ref_status`` attribute
  on its return value to a dictionary mapping ref names
  to error messages. Previously, it raised UpdateRefsError
  if any of the refs failed to update.
  (Jelmer Vernooij, #780)

* Add a ``porcelain.Error`` object that most errors in porcelain
  derive from. (Jelmer Vernooij)

* Fix argument parsing in dulwich command-line app.
  (Jelmer Vernooij, #784)

0.20.3 2020-06-14

* Add support for remembering remote refs after push/pull.
  (Jelmer Vernooij, #752)

* Support passing tree and output encoding to
  dulwich.patch.unified_diff. (Jelmer Vernooij, #763)

* Fix pushing of new refs over HTTP(S) when there are
  no new objects to be sent.
  (Jelmer Vernooij, #739)

* Raise new error HTTPUnauthorized when the server sends
  back a 401. The client can then retry with credentials.
  (Jelmer Vernooij, #691)

* Move the guts of bin/dulwich to dulwich.cli, so it is easier to
  test or import. (Jelmer Vernooij)

* Install dulwich script from entry_points when setuptools is available,
  making it slightly easier to use on Windows. (Jelmer Vernooij, #540)

* Set python_requires>=3.5 in setup.py. (Manuel Jacob)

0.20.2 2020-06-01

* Brown bag release to fix uploads of Windows wheels.

0.20.1 2020-06-01

* Publish binary wheels for: Windows, Linux, Mac OS X.
  (Jelmer Vernooij, #711, #710, #629)

0.20.0 2020-06-01

* Drop support for Python 2. (Jelmer Vernooij)

* Only return files from the loose store that look like git objects.
  (Nicolas Dandrimont)

* Ignore agent= capability if sent by client.
  (Jelmer Vernooij)

* Don't break when encountering block devices.
  (Jelmer Vernooij)

* Decode URL paths in HttpGitClient using utf-8 rather than file system
  encoding. (Manuel Jacob)

* Fix pushing from a shallow clone.
  (Brecht Machiels, #7

(maya)