Environment keys: branch or tag (what triggers it), after (run after another environment), approval (a human must approve), via (deployer), verify, rollback, options.
Verify
Verify runs an HTTP health check after the deploy, with retries: url or url_secret, plus path (default /up), expect (default 200), retries (default 5), delay (seconds, default 10).
If verification fails and rollback is on, the previous release is restored and the job still fails, so a broken deploy is never reported as green.
Rollback re-points the release; it does not undo database migrations. Keep migrations backwards compatible (expand, then contract).
via options, and SSH server setup for a one-time server layout. 
