Merge branch 'rj/branch-in-use-error-message'

A message written in olden time prevented a branch from getting checked out saying it is already checked out elsewhere, but these days, we treat a branch that is being bisected or rebased just like a branch that is checked out and protect it. Rephrase the message to say that the branch is in use. * rj/branch-in-use-error-message: branch: error message checking out a branch in use branch: error message deleting a branch in use