ifMatch

Copies the object if the entity tag (ETag) of the destination object matches the specified tag. If the ETag values do not match, the operation returns a 412 Precondition Failed error. If a concurrent operation occurs during the upload S3 returns a 409 ConditionalRequestConflict response. On a 409 failure you should fetch the object's ETag and retry the upload.

Expects the ETag value as a string.

For more information about conditional requests, see RFC 7232.