Add a function to compare the OS version

[ekohl]

This function aims to reduce the boiler plate that a lot of modules have
to compare versions:

if $facts['operatingsystem'] == 'Ubuntu' && versioncmp(facts['operatingsystemmajrelease'], '16.04') >= 0 {

Can now be reduced to:

if os_version_gte('Ubuntu', '16.04') {

Let the bikeshedding commence!

[david22swan]

@ekohl Your change is failing some syntax checks, just a quick fix needed:

Offenses:
spec/functions/os_version_gte_spec.rb:7:9: C: Style/HashSyntax: Use hash rockets syntax. (https://github.com/bbatsov/ruby-style-guide#hash-literals)
        operatingsystem: 'Debian',
        ^^^^^^^^^^^^^^^^
spec/functions/os_version_gte_spec.rb:8:9: C: Style/HashSyntax: Use hash rockets syntax. (https://github.com/bbatsov/ruby-style-guide#hash-literals)
        operatingsystemmajrelease: '9',
        ^^^^^^^^^^^^^^^^^^^^^^^^^^
spec/functions/os_version_gte_spec.rb:22:9: C: Style/HashSyntax: Use hash rockets syntax. (https://github.com/bbatsov/ruby-style-guide#hash-literals)
        operatingsystem: 'Ubuntu',
        ^^^^^^^^^^^^^^^^
spec/functions/os_version_gte_spec.rb:23:9: C: Style/HashSyntax: Use hash rockets syntax. (https://github.com/bbatsov/ruby-style-guide#hash-literals)
        operatingsystemmajrelease: '16.04',

Otherwise, looks good :)

[david22swan]

@ekohl Unfortunately some random failures have appeared in the spec/functions/to_yaml_spec.rb test file when run on appveyor. They are unrelated to your change however I am unable to merge while they are there, so I won't be able to merge this in until they are dealt with.

[ekohl]

I'm in no hurry :)

[ekohl]

Also realized this will also need docs in README.md I guess.

[david22swan]

@ekohl The stdlib bug was fixed. If you could add some docs I will happily merge.

[david22swan]

@ekohl Hope you don't mind but I added some docs changes myself. If you're ok with them thenI can get this merged.

[ekohl]

Fixed a typo, but otherwise looks good.

[david22swan]

@ekohl ++ :)

[david22swan]

Thanks for the function

[swegener]

The README.md says

Returns:
  - Boolean(0) # When OS is below the given version.
  - Boolean(1) # When OS is equal to or greater than the given version.

but the unit tests and the actual implementation behave like this:

        :operatingsystem => 'Debian',
        :operatingsystemmajrelease => '9',
[...]
    it { is_expected.to run.with_params('Debian', '8').and_return(false) }

Debian 9 is the OS version, but running os_version_gte with Debian 8 returns false.

[ekohl]

Hmm, you may be right. It would have been good to also test for Debian 10. I must admit I did not end up using this function myself. Could you provide a PR to better define the behavior and a bugfix if needed?