We took one pass at this issue in #294, closed by PR #295, but the solution was to just iteratively check a few possibilities. This is more robust and definitely deserved to be included in the code sooner than later, but I can't help but feeling it's not the best permanent solution.

I'm opening this to track an ultimate solution. As I commented here one potential solution might be to clone first and ask questions later: specifically doing a bare clone and just letting Git find the default branch itself, then inspecting what it came up with and using that info to do a checkout.