Multiple identical PUT requests with Transfer-Encoding:diff+If-Match will result in the same thing as a "normal" PUT with an If-Match header - if the resource i

Multiple identical PUT requests with Transfer-Encoding:diff+If-Match will result in the same thing as a "normal" PUT with an If-Match header - if the resource is in the matched state it will be transformed, and if it isn't it will be unchanged. The Transfer-Encoding:diff+If-Match combo is in effect the same thing as sending the whole data blob, it's just an efficient transfer compression. No different than Transfer-Encoding:gzip; the data sent isn't the data to be stored until its Transfer-Encoding has been reversed.