Add support for visibility parameter when creating / editing repository

[patrickmarabeas]

Add support for the visibility parameter when creating or editing a repository.

Currently this has only been implemented at:
a) an organisational permission level
b) filtering when listing repositories

API: https://developer.github.com/v3/repos/#parameters-4

UI: https://help.github.com/en/github/creating-cloning-and-archiving-repositories/creating-a-new-repository

NOTE: This parameter should overwrite the private parameter when both are used.

Happy to pick this issue up if I haven't missed anything obvious.

[gmlewis]

Thank you for the report, @patrickmarabeas.

For your highlighted note, the GitHub docs say:

The visibility parameter overrides the private parameter when you use both parameters with the nebula-preview preview header.

so it won't be necessary to take any extra action when visibility is populated.

I'm thinking that the cleanest solution at this point is to add a new

Visibility *string `json:"visibility,omitempty"`

field to the Repository struct in repos.go at the very end near line 124, and add a comment that this field is only used for the Create and Edit endpoints, and that its use overrides the value of the private field.

Then additionally, this same field would need to be added to the createRepoRequest struct probably right after the Private field on line 298 and it also needs to be copied over after line 336.

Sure, it would be great to have you pick up this issue. Thanks again!