[spree-user] Customizing extension work flow

Ok, this may be a bit basic, but what are the best practices for
customizing an existing extension?

Here's what I'm thinking:

Fork the repo
clone my fork and setup an upstream remote to the original repo

Now, as I'm making modifications, what's the best work flow? Do I include
my forked repo as a gem in my Gemfile. That means any changes I make to the
extension I have to commit locally and push to my remote repo, then switch
over to my spree app and bundle update gem before I can see the results of
the changes.

Or, do I copy the extension from my cloned local repo directly into my
spree app? That means I reference it in my gemfile using the path, make all
my modifications in this embedded gem, then copy the changes back to my
local repo and push them to my forked repo. Finally I'd have to delete the
copied repo from my spree app and update my gemfile to use my remote forked
repo. This is a lot of work for what might amount to some pretty minor
changes. That also means all my changes are in one commit, unless I take
time to break them up when I'm moving them from the embedded version to the
local repo.

Any other ways to do it? I even considered using 'bundle open extension'.
Can you work directly on a gem that way and see the changes? Then how do I
get those changes to my fork?

So how is everyone else doing it?

Thanks for your help. I'm hoping to give more back to the Spree community!

John