coreos/etcd — pull request #1082 by jonboulle (2014-09-17 23:21:49+00:00)
Title: X-Etcd-Index returns the node's modifiedIndex

It used to return the _current_ etcd index. There's little value in returning the modifiedIndex as it's already included in the JSON response. Having the _current_ etcd index is crucial for watching keys.