Improve `script/mirror` argument handling

#!/usr/bin/env bash

# Usage: script/mirror update <COMMIT-RANGE>

#        script/mirror verify <COMMIT-RANGE>

#        script/mirror stats

set -e

commit_range="${1?}"

eval "$(grep RUBY_BUILD_MIRROR_URL= ./bin/ruby-build | head -1)"

help_text() {

  sed -ne '/^#/!q;s/.\{1,2\}//;1d;p' < "$0"

}

test_mirrored() {

  curl -qsSfIL "$RUBY_BUILD_MIRROR_URL/$1" >/dev/null 2>&1

}

  echo "$confirmed/$total mirrored"

}

cmd="${1?}"

cmd="$1"

case "$cmd" in

update | verify | stats )

  shift 1

  "$cmd" "$@"

  ;;

-h | --help )

  help_text

  exit 0

  ;;

* )

  help_text >&2

  exit 1

  ;;

esac