* header when GETs/HEADs of the destination file are made.
* Backends that don't support file metadata will ignore this.
* See http://tools.ietf.org/html/rfc6266 (since 1.20).
- * - headers : If supplied, the backend will return these headers when
- * GETs/HEADs of the destination file are made. Header values
- * should be smaller than 256 bytes, often options or numbers.
+ * - headers : If supplied with a header name/value map, the backend will
+ * reply with these headers when GETs/HEADs of the destination
+ * file are made. Header values should be smaller than 256 bytes.
* Existing headers will remain, but these will replace any
* conflicting previous headers, and headers will be removed
* if they are set to an empty string.