Log Message:
py-pygit2: update to 0.28.0.

Add test target.

0.28.0 (2019-03-19)
-------------------------

- Upgrade to libgit2 0.28
  `#878 <https://github.com/libgit2/pygit2/issues/878>`_

- Add binary wheels for Linux
  `#793 <https://github.com/libgit2/pygit2/issues/793>`_
  `#869 <https://github.com/libgit2/pygit2/pull/869>`_
  `#874 <https://github.com/libgit2/pygit2/pull/874>`_
  `#875 <https://github.com/libgit2/pygit2/pull/875>`_
  `#883 <https://github.com/libgit2/pygit2/pull/883>`_

- New ``pygit2.Mailmap``, see documentation
  `#804 <https://github.com/libgit2/pygit2/pull/804>`_

- New ``Repository.apply(...)`` wraps ``git_apply(..)``
  `#841 <https://github.com/libgit2/pygit2/issues/841>`_
  `#843 <https://github.com/libgit2/pygit2/pull/843>`_

- Now ``Repository.merge_analysis(...)`` accepts an optional reference parameter
  `#888 <https://github.com/libgit2/pygit2/pull/888>`_
  `#891 <https://github.com/libgit2/pygit2/pull/891>`_

- Now ``Repository.add_worktree(...)`` accepts an optional reference parameter
  `#814 <https://github.com/libgit2/pygit2/issues/814>`_
  `#889 <https://github.com/libgit2/pygit2/pull/889>`_

- Now it's possible to set SSL certificate locations
  `#876 <https://github.com/libgit2/pygit2/issues/876>`_
  `#879 <https://github.com/libgit2/pygit2/pull/879>`_
  `#884 <https://github.com/libgit2/pygit2/pull/884>`_
  `#886 <https://github.com/libgit2/pygit2/pull/886>`_

- Test and documentation improvements
  `#873 <https://github.com/libgit2/pygit2/pull/873>`_
  `#887 <https://github.com/libgit2/pygit2/pull/887>`_

Breaking changes:

- Now ``worktree.path`` returns the path to the worktree directory, not to the
  `.git` file within
  `#803 <https://github.com/libgit2/pygit2/issues/803>`_

- Remove undocumented ``worktree.git_path``
  `#803 <https://github.com/libgit2/pygit2/issues/803>`_

0.27.4 (2019-01-19)
-------------------------

- New ``pygit2.LIBGIT2_VER`` tuple
  `#845 <https://github.com/libgit2/pygit2/issues/845>`_
  `#848 <https://github.com/libgit2/pygit2/pull/848>`_

- New objects now support (in)equality comparison and hash
  `#852 <https://github.com/libgit2/pygit2/issues/852>`_
  `#853 <https://github.com/libgit2/pygit2/pull/853>`_

- New references now support (in)equality comparison
  `#860 <https://github.com/libgit2/pygit2/issues/860>`_
  `#862 <https://github.com/libgit2/pygit2/pull/862>`_

- New ``paths`` optional argument in ``Repository.checkout()``
  `#858 <https://github.com/libgit2/pygit2/issues/858>`_
  `#859 <https://github.com/libgit2/pygit2/pull/859>`_

- Fix speed and windows package regression
  `#849 <https://github.com/libgit2/pygit2/issues/849>`_
  `#857 <https://github.com/libgit2/pygit2/issues/857>`_
  `#851 <https://github.com/libgit2/pygit2/pull/851>`_

- Fix deprecation warning
  `#850 <https://github.com/libgit2/pygit2/pull/850>`_

- Documentation fixes
  `#855 <https://github.com/libgit2/pygit2/pull/855>`_

- Add Python classifiers to setup.py
  `#861 <https://github.com/libgit2/pygit2/pull/861>`_

- Speeding up tests in Travis
  `#854 <https://github.com/libgit2/pygit2/pull/854>`_

Breaking changes:

- Remove deprecated `Reference.get_object()`, use `Reference.peel()` instead

0.27.3 (2018-12-15)
-------------------------

- Move to pytest, drop support for Python 3.3 and cffi 0.x
  `#824 <https://github.com/libgit2/pygit2/issues/824>`_
  `#826 <https://github.com/libgit2/pygit2/pull/826>`_
  `#833 <https://github.com/libgit2/pygit2/pull/833>`_
  `#834 <https://github.com/libgit2/pygit2/pull/834>`_

- New support comparing signatures for (in)equality

- New ``Submodule.head_id``
  `#817 <https://github.com/libgit2/pygit2/pull/817>`_

- New ``Remote.prune(...)``
  `#825 <https://github.com/libgit2/pygit2/pull/825>`_

- New ``pygit2.reference_is_valid_name(...)``
  `#827 <https://github.com/libgit2/pygit2/pull/827>`_

- New ``AlreadyExistsError`` and ``InvalidSpecError``
  `#828 <https://github.com/libgit2/pygit2/issues/828>`_
  `#829 <https://github.com/libgit2/pygit2/pull/829>`_

- New ``Reference.raw_name``, ``Reference.raw_shorthand``, ``Tag.raw_name``,
  ``Tag.raw_message`` and ``DiffFile.raw_path``
  `#840 <https://github.com/libgit2/pygit2/pull/840>`_

- Fix decode error in commit messages and signatures
  `#839 <https://github.com/libgit2/pygit2/issues/839>`_

- Fix, raise error in ``Repository.descendant_of(...)`` if commit doesn't exist
  `#822 <https://github.com/libgit2/pygit2/issues/822>`_
  `#842 <https://github.com/libgit2/pygit2/pull/842>`_

- Documentation fixes
  `#821 <https://github.com/libgit2/pygit2/pull/821>`_

Breaking changes:

- Remove undocumented ``Tag._message``, replaced by ``Tag.raw_message``