Adding the binary diff flag GIT_DIFF_SHOW_BINARY to pygit2.
libgit2 0.23.0 already supports this constant to be used in diff
flags and produces properly formated binary diffs.
The current hierarchy of test cases that create and blow away test
repositories in the ``setUp`` and ``tearDown`` methods is inadequate
for testing scenarios where multiple repositories must be edited,
e.g. testing push.
Extract the temporary repository behaviour into a context manager
class ``TemporaryRepository`` which can be used via the ``with``
keyword. The context manager's ``__enter__` method returns creates
the specified repository in a temporary directory and returns its
path. The temporary directory is removed in ``__exit__``.
Update the existing test case base classes to use the context
manager and invoke ``__enter__`` and ``__exit__`` in the ``setUp``
and ``tearDown`` methods respectively.
Finally, make some small tweaks to a handful of tests to get them
working under this new system.
There were two problems:
- Windows refuses to remove a file that is in use. Solution, close
the repo before cleaning the temporary directory.
- Windows refuses to remove a read-only file. Solution, change mode
to writable.
- create_repository
- IndexEntry.path
- Correct SHAs in Index iteration
- Opening a bare index & attempting to add to it
- Walker.reset
- Walker.push
- Walker.sort
