My product (https://gitsense.com) moves most of Git's history into a Postgres database and from there, you can execute the following SQL statement:

    select
        commit_ym AS month,
        count(distinct(author_email)) as authors,
        count(distinct(commit_id)) as commits,
        count(distinct(path_id)) as files,
        sum(total) as churn
    from
        z1_commits_422 as commits,
        z1_changes_422 as changes,
        z1_code_churn_422 as churn
    where
        commits.id=changes.commit_id and
        changes.code_churn_id=churn.id and
        lang='java'
    group by commit_ym
    order by commit_ym desc
    limit 12

By having most of Git's history in SQL, I can slice, dice and cross-reference code history, which is how my product works.