pub fn acquire_data_dir_lock(data_dir: &Path) -> Result<(), String>Expand description
Take srv’s exclusive lock on data_dir (<data_dir>/srv.lock): one srv per
set of databases, however each was started — launcher, host or --headless
(SPEC_SRV_HEADLESS_MODE §3.2; Codex P1 on #3893). Idempotent within a
process, so headless setup can take it early and bootstrap again later.
Advisory flock on Unix; not exclusive elsewhere (see MuxLock).