Junio C Hamano [off-list ref] writes:
... I suspect that calling interpret_empty_at() from
that function is fundamentally flawed. The "@" end user types never
means refs/heads/HEAD, and HEAD@{either reflog or -1} would not mean
anything that should be taken as a branch_name, either.
The latter should read "HEAD@{either reflog or -1 or 'upstream'}"
Or do we make HEAD@{upstream} to mean "deref HEAD to learn the
current branch name and then take its upstream"? If so @@{upstream}
might logically make sense, but I do not see why @{upstream} without
HEAD or @ is not sufficient to begin with, so...