message: Use ls-remote to get default branch
  Calling GitHub API on macOS without the token hits rate limit
diff: @@ -4,7 +4,7 @@ fetch_brew_tap() {
  tap_user=$(dirname "$tap")
  tap_name=$(basename "$tap")
  mkdir -p "$tap_dir/$tap_user"
  - branch="$(get -s -n "" "https://api.github.com/repos/$tap" | grep default_branch | cut -d: -f 2 | grep -Eo '[^\", ]+' | tr -d '\n')"
  + branch="$(git ls-remote --symref "https://github.com/$tap" HEAD | grep -Eo 'refs/heads/.*' | tr '\t' '\n' | head -1 | cut -d '/' -f 3)"
  get -s -n "" "https://github.com/$tap/archive/$branch.tar.gz" | sudo tar -xzf - -C "$tap_dir/$tap_user"
  sudo mv "$tap_dir/$tap_user/$tap_name-$branch" "$tap_dir/$tap_user/$tap_name"
  }
  