git author is the committer

[natestedman]

In git.py you're doing:

    return Commit(commit.id, commit.committer,
        datetime.fromtimestamp(commit.commit_time), commit.message, files,
        lambda: generate_unified_diff(self, files, parent, commit.id))

But this sets the author of the commit to the committer, which isn't always the case. It should be:

    return Commit(commit.id, commit.author,
        datetime.fromtimestamp(commit.commit_time), commit.message, files,
        lambda: generate_unified_diff(self, files, parent, commit.id))