http://www.rfc-editor.org/rfc/rfc8144.txt
RFC 8144: Use of the Prefer Header Field in Web Distributed Authoring and Versioning (WebDAV), K. Murchison2017-04-01T23:00:00-00:00This document defines how the Prefer header field (RFC 7240) can be used by a Web Distributed Authoring and Versioning (WebDAV) client to request that certain behaviors be employed by a server while constructing a response to a request. Furthermore, it defines the new "depth-noroot" preference.