Merge branch 'jc/worktree-add-short-help'

Error message fix. * jc/worktree-add-short-help: worktree: say that "add" takes an arbitrary commit in short-help

Junio C Hamano committed Feb 15, 2018 at 14:55 UTC cc7655a5a3465ccce2c84379721dd1cbdd57faa9

No changes.