GSS-TSIG does not work on v0.7.6 even though the doc says it does

[ba-work]

What happened:
tried to run with gss-tsig as documented here (note the deployment specifically has image: k8s.gcr.io/external-dns/external-dns:v0.7.6) and it does not work:

$ docker run k8s.gcr.io/external-dns/external-dns:v0.7.6 --rfc2136-gss-tsig
$ time="2021-03-02T18:23:34Z" level=fatal msg="flag parsing error: unknown long flag '--rfc2136-gss-tsig'"

What you expected to happen:
gss-tsig works.

How to reproduce it (as minimally and precisely as possible):
use the --rfc2136-gss-tsig flag. (it also doesn't show in --help)

Anything else we need to know?:
if you switch to the tag v0.7.6 the gss-tsig documentation is gone, suggesting this is not available yet

Environment:

• External-DNS version (use external-dns --version): v0.7.6
• DNS provider: ad dns
• Others:

[kundan2707]

/assign

[kundan2707]

--rfc2136-host=""             When using the RFC2136 provider, specify the
                                host of the DNS server
  --rfc2136-port=0              When using the RFC2136 provider, specify the
                                port of the DNS server
  --rfc2136-zone=""             When using the RFC2136 provider, specify the
                                zone entry of the DNS server to use
  --rfc2136-insecure            When using the RFC2136 provider, specify whether
                                to attach TSIG or not (default: false, requires
                                --rfc2136-tsig-keyname and rfc2136-tsig-secret)
  --rfc2136-tsig-keyname=""     When using the RFC2136 provider, specify the
                                TSIG key to attached to DNS messages (required
                                when --rfc2136-insecure=false)
  --rfc2136-tsig-secret=""      When using the RFC2136 provider, specify the
                                TSIG (base64) value to attached to DNS messages
                                (required when --rfc2136-insecure=false)
  --rfc2136-tsig-secret-alg=""  When using the RFC2136 provider, specify the
                                TSIG (base64) value to attached to DNS messages
                                (required when --rfc2136-insecure=false)
  --rfc2136-tsig-axfr           When using the RFC2136 provider, specify the
                                TSIG (base64) value to attached to DNS messages
                                (required when --rfc2136-insecure=false)
  --rfc2136-min-ttl=0s          When using the RFC2136 provider, specify minimal
                                TTL (in duration format) for records. This value
                                will be used if the provided TTL for a
                                service/ingress is lower than this

[kundan2707]

https://github.com/kubernetes-sigs/external-dns/blob/master/docs/tutorials/rfc2136.md#external-dns-configuration-1 needs correction.
I am updating external-dns configuration section withh correct sets of arguments

[InputObject2]

The --rfc2136-gss-tsig was added with the addition of the Windows DNS support in rfc2136, it should stay in the docs for master as the code is present there as well. The whole Windows+kerberos section doesn't work without that flag.

The flag isn't present in release 0.7.6 yet, you either need to build it yourself (using master) or wait for 0.7.7, I'd guess.