Support for github assets based on branches/revisions

[DragosDumitrache]

:person_frowning: Problem Statement

Currently, github_asset seems to only support getting assets based on a tag, which involves a release happening. If I wanted to test a feature across repos, I would have to cut a new release from that feature branch, or that feature branch being merged into HEAD, updating the revision tag for the cookbook, running my integration tests, and repeat the cycle if any issues crop up.

:grey_question: Possible Solution

Add support for specifying a branch/revision and using octokit to check out the code and the needed files at that point in time, as an alternative to tags.

:arrow_heading_up: Describe alternatives you've considered

The alternative would be a draft release, which is something I'll trial shortly, but it still involves a potential draft release for something that might not be ready.

I'd love to get your thoughts on the matter though, and whether this is feasible or not.