commits = parse_gitlog(pipe)
commits_by_date_author = groupby(commits, key=lambda x: (x.date, x.author))
for (date, author), commits in commits_by_date_author:
commits = parse_gitlog(pipe)
commits_by_date_author = groupby(commits, key=lambda x: (x.date, x.author))
for (date, author), commits in commits_by_date_author: