R1:06edcf270921

Fix an issue where ancestors of permanent refs might not be published during import or if a branch is later made permanent

Summary:
Fixes T13284. See that task for substantial discussion. There are currently two cases where we'll skip over commits which we should publish:

- if a branch is not permanent, then later made permanent; or
- in some cases, the first time we examine branches in a repository.

In both cases, this error is one-shot and things work correctly going forward. The root cause is…