hg --close-branch updates tip :-(

Here's something joyful: when you close a branch in Mercurial, e.g. via

  hg update -C branch-to-be-closed
  hg commit --close-branch -m 'branch to be closed'

it becomes the "tip" - the most recent changest.

Many tools confuse "tip" with something like "the tip of the default branch".  And do stuff like checking out or diffstat'ing with tip.

Which probably is not what you want for a closed branch.