feat(ssh_known_hosts): allow to omit IP addresses

[alxwr]

PR progress checklist (to be filled in by reviewers)

• [ ] Changes to documentation are appropriate (or tick if not required)
• [ ] Changes to tests are appropriate (or tick if not required)
• [ ] Reviews completed

---

What type of PR is this?

Primary type

• [ ] [build] Changes related to the build system
• [ ] [chore] Changes to the build process or auxiliary tools and libraries such as documentation generation
• [ ] [ci] Changes to the continuous integration configuration
• [x] [feat] A new feature
• [ ] [fix] A bug fix
• [ ] [perf] A code change that improves performance
• [ ] [refactor] A code change that neither fixes a bug nor adds a feature
• [ ] [revert] A change used to revert a previous commit
• [ ] [style] Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc.)

Secondary type

• [x] [docs] Documentation changes
• [x] [test] Adding missing or correcting existing tests

Does this PR introduce a BREAKING CHANGE?

No.

Related issues and/or pull requests

Describe the changes you're proposing

Servers like github.com are hosted on multiple IP addresses. When the IP address is retrieved via DNS this leads to a flapping /etc/ssh/ssh_known_hosts. To prevent that fluctuation the Pillar openssh:known_hosts:omit_ip_address was introduced. It can either specify a list of hosts or True.

Pillar / config required to test the proposed changes

I updated test/salt/pillar/default.sls.

Debug log showing how the proposed changes work

host:                                                                                              
----------                                                                                                            
          ID: manage ssh_known_hosts file                                                                             
    Function: file.managed                                                                                            
        Name: /etc/ssh/ssh_known_hosts                                                                                
      Result: None                                                                                                    
     Comment: The file /etc/ssh/ssh_known_hosts is set to be changed                                                  
              Note: No changes made, actual changes may                                                               
              be different due to other states.                                                                       
     Started: 17:07:06.729371                                                                                         
    Duration: 2172.67 ms                                                                                              
     Changes:                                                                                                         
              ----------                                                                                              
              diff:                                                                                                   
                  ---                                                                                                 
                  +++ 
                  @@ -29,6 +29,7 @@
                   […]
                  -github.com,140.82.118.3,140.82.118.4 ssh-rsa AAAAB3NzaC1yc2E[…] git@github.com
                  +github.com ssh-rsa AAAAB3NzaC1yc2E[…] git@github.com
                   […]

Documentation checklist

• [x] Updated the README (e.g. Available states).
• [x] Updated pillar.example.

Testing checklist

• [ ] Included in Kitchen (i.e. under state_top).
• [x] Covered by new/existing tests (e.g. InSpec, Serverspec, etc.).
• [x] Updated the relevant test pillar.

Additional context

[myii]

@alxwr Now you're going to get bitten by commitlint!

-chore(README): use in YAML examples
+docs(readme): use in YAML examples

(Not the chore itself but the commit scope must be lowercase).

[myii]

@alxwr Since we can get around the commitlint violation upon (squash and) merge, I've just done that here. Thanks for the contribution. Thanks @aboe76 for the review, as well.

[saltstack-formulas-travis]

:tada: This PR is included in version 0.43.0 :tada:

The release is available on GitHub release

Your semantic-release bot :package::rocket:

[alxwr]

Thanks @myii and @aboe76 !