The upgrade service reads BRANCH from /tmp/wrolpi-upgrade.env, which upgrade.sh removes when it finishes. The
Controller wrote that file only when a request had parameters, so starting an upgrade without a branch (the simple UI
sends no body when the field is empty) left the service unable to start, while the API answered success. A request
like {"branch": "master"} was accepted with the key ignored, the same way.
Now the env file is always written, and a missing branch is the current one, as upgrade.sh chooses; a file left by an
interrupted run no longer chooses it. Unknown parameters and unknown request keys are errors.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
