When running the publish workflow, either via the command line or
via the daily cron job, we should use a constant SHA instead of
whatever happens to be at the head of the main branch at the time the
workflow is run.
The difference is subtle: currently, the SHA is read at runtime,
each time the workflow is run. With this change, the SHA is read right
before the workflow is created and passed in as a constant parameter.
In practical terms, this means if a workflow is re-run via the CircleCI
web UI, it will always re-run using the same commit SHA as the original
workflow, instead of fetching the latest SHA from GitHub, which may
have changed.
Also avoids a race condition where the head SHA changes in between the
Next publish job and the Experimental publish job.
```
yarn publish-prereleases
```
Script to trigger a CircleCI workflow that publishes preleases.
**The CI workflow doesn't actually publish yet; it just runs and logs
its inputs.**
Brian Vaughn