create-pr: enable specifing the draft mode

[TomasTomecek]

If PR title starts with 'WIP', use draft mode.

[Toaster192]

Doesn't seem to be implemented yet by pyGithub https://pygithub.readthedocs.io/en/latest/github_objects/Repository.html?highlight=draft#github.Repository.Repository.create_pull
API:
https://developer.github.com/v3/pulls/#input

That means not even moving to ogr would welp? (without doing a manual API call)

[lachmanfrantisek]

Yes, It is currently possible only with custom media type in header:

Note: The Draft Pull Request API is currently available for developers to preview. You can use this API to create a draft pull request or see whether a pull request is in draft state. See the blog post preview for more details. To access the new draft parameter during the preview period, you must provide a custom media type in the Accept header:
application/vnd.github.shadow-cat-preview

I'm not sure if we can force PyGithub to use it. (If I remember correctly, editing header on the PyGithub site would be hard as well. So we need to wait for the stable API.)

[TomasTomecek]

...and sadly PyGithub is kinda-dead -- a lot of pull requests with no response or a lack of feedback

I think it should be possible to inherit from a pygithub class and change the headers like that: or send a PR and fix it in their codebase.