unison doesn't include unison-fsmonitor for macOS, thus -repeat watch option doesn't work out of the box. This utility fills the gap.
cargo build --release
ln -s $PWD/target/release/unison-fsmonitor /usr/local/bin/
cargo build
ln -s $PWD/target/debug/unison-fsmonitor /usr/local/bin/
RUST_LOG=debug unison