'determineOriginAndMain' can fail after decolinization

[zanerock]

Overview

If the origin remote has branch master and then switches to use main as the default branch, then the local view of origin branches will contain both as the general fetch/pull process is only additive and does not delete.

Deliverables

• In the face of 'multiple main branches', run git remote update ${origin} --prune and re-try (and then really give up and throw an exception on the retry if the problem persists).

Notes

https://stackoverflow.com/questions/36358265/when-does-git-refresh-the-list-of-remote-branches