Repository.apply causes segfaults or assertion failures when anything except a Diff is passed in

[MathSquared]

The apply method of a Repository fails ungracefully when I give it anything other than a Diff object. Specifically, when I pass in a Patch, the assertion (repo && diff) fails, even though the documentation says apply can accept a diff or a patch. When I pass in a string, the application simply segfaults.

Repro:

from pygit2 import Repository
r = Repository('path/to/repository')
r.apply('foo')  # segfault

Though I use 'foo' in this test, the same result arises if I pass in the string form of a Git diff.

I would expect pygit2 to coerce a string or Patch to a Diff, or at least to raise a Python exception instead of allowing the C backend to throw an error and crash the application.

[jdavid]

The segfault was already reported in issue #1033 and fixed with commit 23a4dd6, which has been released in v1.3.0

Traceback (most recent call last):
  File "issue1037.py", line 3, in <module>
    r.apply('foo')  # segfault
TypeError: argument 1 must be _pygit2.Diff, not str

In commit 9d7e512 I've fixed the documentation.

Regarding coercing to a Diff, PRs are welcome.