repoview: improve performance for computehidden (issue4206) For repos with a large number of heads (including hidden heads), a stale tag cache would cause computehidden to be drastically slower because of a the call to repo.tags() (which would build the tag cache). We actually don't need the tag cache for computehidden because we filter out global tags. This patch replaces the call to repo.tags with readlocaltags so as to avoid the tag cache.