How does "local_seq" design doc option work?

Could someone explain the "local_seq" design doc option? I've had a request to implement it in TouchDB, but
I don't know what it does. The only info about it I can find is the Jira issue COUCHDB-346*, which describes
adding that property to the "options" object of a design doc, but it doesn't say what exactly it does.
There's no link to a patch, either.

I've experimented by adding this option to a design doc in CouchDB 1.2, but no matter how I query the view —
like adding "?include_docs=true&update_seq=true&local_seq=true" to the URL — I don't see sequence
numbers appearing in the response.

As usual, I promise to add what I've learned to the CouchDB wiki. :)

—Jens

* https://issues.apache.org/jira/browse/COUCHDB-346