The following examples assume you already have a repository in place to work with. If not, see git-init.

If you want to stage (add) a file in a repository that is checked out to the file system, you can stage a file with changes like so:

using (var repo = new Repository("path/to/your/repo"))
{
    // Stage the file
    repo.Index.Add("file/with/changes.txt");
}

$ git add --all .

using (var repo = new Repository("path/to/your/repo"))
{
    Commands.Stage(repo, "*");
}