Staging and production deployments are automated by a deployer service created and maintained by @github/docs-engineering.
When a pull request contains only content changes, it can be previewed without a deployment. Code changes will require a deployment. GitHub Staff can deploy such a PR to a staging environment.
Docs uses merge queue.
When a pull request is merged to the repo's default branch, it is automatically deployed to production and the status is displayed on the PR's page on github.com. It can take up to 24 hours for changes to be visible on the site.
After a PR is closed, the branch is automatically deleted. This does not affect the deployment process.