Auto-merging blessed branches is stopped

[Nicholas Skaggs]

With the changes to parallelism, revision results is no longer used. This was used by the github-merge-branches build job to automerge blessed branches. A suitable replacement job needs to be found in order to execute this job.

[Aaron Bentley (abentley)]

Here are the options I see:
- We can manually trigger github-merge-branches on the rare occasion that there is a bless.
- The update-outcome script can trigger github-merge-branches when there is a bless.
  - This will happen before the reports site is updated
  - We may need to work to prevent github-merge-branches from being called multiple times
  - This prevents us from using outcome analyser in determining a bless
- The get-s3-ci-results script can trigger github-merge-branches when there is a bless
  - This will happen roughly simultaneously with updating the report
  - We may need to work to prevent github-merge-branches from being called multiple times
  - This allows us to use outcome analyser in determining a bless
- We can add a REST API to the reports site.
  - github-merge-branches would use the API to determine the last blessed build
  - github-merge-branches would run periodically, and exit early most of the time.

1. The update-outcome script can trigger

[Aaron Bentley (abentley)]

Sorry, ignore 1.

[Nicholas Skaggs (nskaggs)]

While manual works for now, I'd like to see something trigger this job as before. It seems like nothing proposed is a trivial fix, so while I don't think this "feature" necessitates extra work, I'm guessing we'll want other jobs to key off blessed/cursed builds in the future. Perhaps not.