ifNoneMatch

Uploads the object only if the object key name does not already exist in the bucket specified. Otherwise, Amazon S3 returns a 412 Precondition Failed error.

If a conflicting operation occurs during the upload S3 returns a 409 ConditionalRequestConflict response. On a 409 failure you should retry the upload.

Expects the '*' (asterisk) character.

For more information about conditional requests, see RFC 7232, or Conditional requests in the Amazon S3 User Guide.