Merge branch 'tg/worktree-create-tracking'

The way "git worktree add" determines what branch to create from where and checkout in the new worktree has been updated a bit. * tg/worktree-create-tracking: add worktree.guessRemote config option worktree: add --guess-remote flag to add subcommand worktree: make add <path> <branch> dwim worktree: add --[no-]track option to the add subcommand worktree: add can be created from any commit-ish checkout: factor out functions to new lib file