arcfour256
arcfour128
arcfour
aes128-cbc
3des-cbc
```

`--sftp=mac-algos=...` specifies a default set of MAC algorithms in preference order.
This is based on RFC 4253, section 6.4, but with hmac-md5 variants removed because they have 
reached the end of their useful life.

Valid values: 

```
******@****.***
******@****.***
hmac-sha2-256
hmac-sha2-512
hmac-sha1

// with control characters, this is a specialized extension
// to support AWS S3 compatible behavior.
//
// Do not use this function for anything other than ListObjects()
// variants, please open a github discussion if you wish to use
// this in other places.
func encodeResponseList(response interface{}) []byte {
	var buf bytes.Buffer
	buf.WriteString(xxml.Header)