Create new branch for worktree if it doesn't exist

worktree/worktree.plugin.zsh

@@ -33,7 +33,11 @@ Manage git worktrees by branch name."
     add)
       local root=$(git rev-parse --show-toplevel)
       local wt_dest=${root:h}/${root:t}@${branch}
-      git worktree add "$wt_dest" "$branch"
+      if ! git show-ref --verify --quiet refs/heads/"$branch" && \
+         ! git show-ref --verify --quiet refs/remotes/origin/"$branch"; then
+        git branch "$branch" origin/main || return 1
+      fi
+      git worktree add "$wt_dest" "$branch" || return 1
       if [ -f $root/.enter ] && [ -f $root/.exit ]; then
         ln -s $root/.enter $wt_dest/.enter
         ln -s $root/.exit $wt_dest/.exit