Skip processing already processed files

[kaspth]

This is the hackiest code I've done yet, but I just couldn't do it cleanly for now.

On first run for a file like this:

# tests/seeds/accounts/business.rb
accounts.create :business, name: "Big Business Co."

We both add data in the database and define a accounts.business accessor method, but once we've done that, we don't necessarily need to do it again.

So now we record the methods we add into tmp/oaken-result.yml, and via the file checksum we can see whether we've already processed the file. If we've already processed the file, we can "replay" those previously added methods and add them again.

This way we can skip the entire file because the checksum lets us know we've already handled it.

This is kind of at the edge of my ability to do, so I'm planning on sleeping on this and then keep tweaking the design. I'm also sure there's tons of pitfalls with this, it's not easy!