Adding the upstream branch to your zsh pure theme

pure-theme-plus-git-upstream.sh

# Nothing to do if we aren't in a git repo
if git rev-parse --git-dir > /dev/null 2>&1; then
  # Get the name of upstream
  upstream=$(command git rev-parse --symbolic-full-name --abbrev-ref @{u} 2>/dev/null)

  # Check if we have an upstream, and that it is different than our current branch
  if [[
    $(command git rev-parse --symbolic-full-name --abbrev-ref @{u} 2>/dev/null | sed 's/origin\///')
    != $(command git rev-parse --abbrev-ref HEAD)
    && ! -z "$upstream"
  ]]; then
    upstreamText=" [${upstream}]"
  fi
fi

# Add upstream text to the prompt
preprompt+="%F{$git_color}${vcs_info_msg_0_}${prompt_pure_git_dirty}${upstreamText}%f"