@nulltoken pointed me at [StatusOptions] (https://github.com/libgit2/libgit2sharp/blob/vNext/LibGit2Sharp/StatusOptions.cs#L34-L39). Here is what I did for [merge] (https://github.com/libgit2/libgit2sharp/pull/643/files#diff-4eb1f6f0dcaa357ade26bfb6c2e7dde4R10).