prune: skip already obsolete commits
This makes `hg prune` skip already obsolete commits and just print a message about them, just like how `hg rebase` does. --HG-- branch : stable
This instance will be upgraded to Heptapod 0.19.0rc2 on 2021-01-18 at 11:00 UTC+1 (a few minutes of downtime)
This makes `hg prune` skip already obsolete commits and just print a message about them, just like how `hg rebase` does. --HG-- branch : stable