Correct me if I'm wrong, but wouldn't you then have to make a separate HTTP request for each non-contiguous block of modified lines that you request? Also, wouldn't the client have to know in advance which lines were changed in the new version? Maybe I'm misinformed about how Content-Range works.

Also, in regards to getting a patch every time, Josh Harrison (one of the creators) responds in a comment on the blog post:

  You are correct in noticing that the patched version is
  not cached. However, the v1->v2 patch itself IS cached,
  meaning that the next time the user visits, if there has
  not been a new release, then both v1 and the v1->v2 patch
  are retrieved from cache. Also, we are working on
  incorporating local storage, which would allow the
  updated version to be persisted each time it is patched.