Sort ascending with null values last

Ahoy. When sorting on a string field in ascending order, is there a way to
move the documents with a null value for the sort-field to the end of the
results?

For example, with the setup below, we sort by ascending city, but Bob has
no city and is the first result. Can we cause Bob to be the last result?

curl -s -X DELETE localhost:9200/test
curl -X PUT 'localhost:9200/test?pretty=true'

curl -XPUT localhost:9200/test/people/1 -d '{
"name" : "Jane",
"city" : "Toronto"
}'

curl -XPUT localhost:9200/test/people/2 -d '{
"name": "Jack",
"city": "Ottawa"
}'

curl -XPUT localhost:9200/test/people/3 -d '{
"name": "Bob"
}'

curl 'localhost:9200/test/people/_search' -d '{ sort: [{"city": {"order":
"asc"} }] }'

I created an issue for this some time ago (as I need the feature too):
https://github.com/elasticsearch/elasticsearch/issues/896 (just in case you
want to vote it up ... ;-))

Thanks for the link, Jan. I just commented on it.

The only workaround that I can think of is to modify one's query to exclude
documents with a null value for the sort-field.

Can you think of any other workarounds until #896 is implemented?