_zimfw_upgrade() {
  local zscript=${ZIM_HOME}/<%= script_filename %>
  local zurl=https://raw.githubusercontent.com/zimfw/zimfw/develop/<%= script_filename %>
  if (( ${+commands[wget]} )); then
    command wget -nv ${1} -O ${zscript}.new ${zurl} || return 1
  else
    command curl -fsSL -o ${zscript}.new ${zurl} || return 1
  fi
  if command cmp -s ${zscript}{,.new}; then
    command rm ${zscript}.new && \
        if [[ ${1} != -q ]]; then
          print -P "%F{green}✓%f <%= script_filename %>: Already up to date."
        fi
  else
    command mv ${zscript}{,.old} && command mv ${zscript}{.new,} && \
        if [[ ${1} != -q ]]; then
          print -P "%F{green}✓%f <%= script_filename %>: upgraded. Restart your terminal for changes to take effect."
        fi
  fi
}