This patch adds support for updating to a hidden changeset without using
--hidden if experimental.directacces=True is set. The update command will
print out a warning when updating to a hidden changeset saying:
`updating to a hidden changeset <hash>`
The warning is also printed when directaccess is not used and --hidden is
passed which I think is good behaviour. Tests are added for the directaccess
part and updated output of tests which have case of updating to hidden cset
using --hidden.
filtername == "visible-hidden" doesn't mean ctx is obsolete.
Maybe we can check ctx.hidden()? It's probably okay to warn
hidden working parent no matter if directaccess is enabled or not.