Merge branch 'rj/branch-unborn-in-other-worktrees'

Error messages given when working on an unborn branch that is
checked out in another worktree have been improved.

* rj/branch-unborn-in-other-worktrees:
  branch: avoid unnecessary worktrees traversals
  branch: rename orphan branches in any worktree
  branch: description for orphan branch errors
  branch: use get_worktrees() in copy_or_rename_branch()
  branch: test for failures while renaming branches

diff --cc branch.c
Simple merge

diff --cc builtin/branch.c
Simple merge

diff --cc t/t3200-branch.sh
Simple merge