YETUS-1022. Get commit sha from github PR json

[aw-was-here]

• includes some docs updates to reflect
  what is supported for github

[aw-was-here]

FYI: I don't want to commit this until YETUS-1021 gets in so that it can validate the website changes.

[aajisaka]

Thank you @aw-was-here
I'm testing the PR in apache/hadoop#2348

[aw-was-here]

Argh. Need to rebase to pick up #154's website checker action.

[aajisaka]

The commit status is updated successfully in apache/hadoop#2348

[aw-was-here]

Thanks @aajisaka! Now I just need to make sure the website bits are correct ...

[aajisaka]

(This is not directly related to this issue)

Now the "Details" link is console.
I think it's better for developers to link to the report HTML (ex. https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2348/12/Yetus_20Report/) instead of the console. It can be discussed/implemented in a separate issue.

[aw-was-here]

(This is not directly related to this issue)

Now the "Details" link is console.
I think it's better for developers to link to the report HTML (ex. ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2348/12/Yetus_20Report) instead of the console. It can be discussed/implemented in a separate issue.

It definitely needs to be a separare issue since it means mixing two separate plug-ins. There's no guarantee that htmlout's output is actually reachable either... for example, on here.

[aw-was-here]

Thanks for the review. website changes passed, so I'm merging this in....

[aajisaka]

Thank you @aw-was-here