CloudSandboxStrategy is defined in cloud_aws.py, not cloud.py. The
benchmark was importing it from the wrong module, causing an ImportError
during benchmark discovery.
The benchmark-regression CI job's "Compute base commit" step used
forgejo.base_ref which is empty for push events, causing
`git merge-base HEAD "origin/"` to fail with exit 128. Add a guard
that falls back to HEAD~1 when base_ref is unset.
HAL9000
freemo
