Function get_log 

pub fn get_log(
    repo: &Repository,
    max_count: usize,
    filter_author: Option<&str>,
    filter_message: Option<&str>,
) -> Result<Vec<CommitInfo>>

Retrieve the commit log, optionally filtered by author and/or message substring.

Walks from HEAD, returning at most max_count commits that match every supplied filter (filters are AND-ed together).