macOS's Silent rsync Swap Breaks Repository Automation

This incident reveals how silent system-level tool substitutions can undermine automated infrastructure without warning. When macOS replaced GNU rsync with its BSD-licensed openrsync variant, critical flag compatibility broke—demonstrating that even well-tested scripts depend on subtle behavioral differences. For developers relying on automation for deployments, backups, or repository synchronization, the story underscores the importance of explicit tool validation and cross-implementation compatibility testing.