shell> curl -X PUT --header 'If-Match: "715715467"' --data-binary @- --dump - http://localhost:8529/_api/document/products/715387787 <<EOF
{"other":"content"}
EOF

HTTP/1.1 412 Precondition Failed
content-type: application/json; charset=utf-8
etag: "715387787"

{ 
  "error" : true, 
  "code" : 412, 
  "errorNum" : 1200, 
  "errorMessage" : "precondition failed", 
  "_id" : "products/715387787", 
  "_rev" : "715387787", 
  "_key" : "715387787" 
}