Rails offline development with CDN

Question

I love to develop without the internet. But the problem is we cannot get image/css/javascript assets files by CDN.

I think the best way is

• On development env, try to get such asset files from CDN first, and
  • If possible, use it and cache it
  • If impossible, use cache

Alternative is

• Keep all such asset files in the repo too
• Use them on development env, use CDN on production env

But implementing these takes a bit time and I believe many developers face this problem.

So I want to know your way to solve this problem. If any good gem, it's fantastic.

My env is Rails4 without assets pipeline nor turbolinks.