Function msg_fs_sync_excluding 

pub fn msg_fs_sync_excluding(
    nonce: u16,
    flags: u16,
    latency_ms: u16,
    inline_max: u32,
    path: &str,
    exclude: &str,
) -> Vec<u8> 

Build a C2S_FS_SYNC carrying client exclude patterns: gitignore syntax, one per line, anchored at the sync root (docs/design/fs-watch.md “Ignoring”). Sets FS_SYNC_EXCLUDE; an empty exclude builds the plain form instead, so a caller need not special-case “no patterns”.