Function svn_auth_get_parameter 

pub unsafe extern "C" fn svn_auth_get_parameter(
    auth_baton: *mut svn_auth_baton_t,
    name: *const c_char,
) -> *const c_void

Get an authentication run-time parameter.

Return a value for run-time parameter @a name from @a auth_baton. Return NULL if the parameter doesn’t exist.