Merge branch 'sn/rebase-update-refs-symrefs' into seen

Merge branch 'sn/rebase-update-refs-symrefs' into seen

"git rebase --update-refs" has been taught to resolve local branch
symrefs to their referents before queuing updates. This correctly
skips aliases of the current branch and avoids duplicate updates for
underlying real branches, fixing failures when branch aliases (like a
default branch rename) are present.

* sn/rebase-update-refs-symrefs:
  rebase: skip branch symref aliases
  t3404: add failing branch symref test