google/go-github — pull request #121 by grobie (2014-06-12 01:26:41+00:00)
Title: Fix CreateCommit

The input and response types for commit messages differ in the API.
While commit.Tree and commit.Parents are objects with fields when
returned by the GitHub API, the attributes are plain strings when
creating new commits.

See: https://developer.github.com/v3/git/commits/#create-a-commit

I have no idea how this could have worked before, I assume it has always been broken so far?