Function install_new_file 

pub fn install_new_file(
    directory: &File,
    source_name: &OsStr,
    target_name: &OsStr,
) -> Result<()>

Atomically install a new regular file without replacing an existing entry.

Windows uses the same flushed write-through source handle for the NTFS namespace rename. POSIX callers remain responsible for directory fsync.