apply has been merged to libgit2 in this PR.
This issue is about exposing it to pygit2.

One way is to support repository.apply(diff), e.g.

with open(path, 'r') as f:
    patch = f.read()

repo.apply(pygit2.Diff.parse_diff(patch))

I already have a patch for this (src/repository.*) and I am in the process of adding unit tests to it.

Is this something worth and that I should continue to put efford on?