Function git_commit_in_repo 

pub fn git_commit_in_repo(
    repo_root: &Path,
    message: &str,
    git_user_name: Option<&str>,
    git_user_email: Option<&str>,
    executor: Option<&dyn ProcessExecutor>,
) -> Result<Option<Oid>>

Create a commit in the repository discovered from repo_root.

This avoids relying on process-wide CWD and allows callers to select the repository to operate on.