Function stash_binary 

pub fn stash_binary(
    exe: &Path,
    app_root: &Path,
    pointer: Option<Option<&str>>,
    require_marker: bool,
) -> Result<PathBuf>

The stash copy itself. pointer is Some(<pointer file override>) to write the pointer file, None to leave it alone; require_marker keeps the QA control-marker check (an explicitly named UI binary skips it, as before, and passes false). The caller has already refused installed apps.