Function svn_auth_set_parameter 

pub unsafe extern "C" fn svn_auth_set_parameter(
    auth_baton: *mut svn_auth_baton_t,
    name: *const c_char,
    value: *const c_void,
)

Set an authentication run-time parameter.

Store @a name / @a value pair as a run-time parameter in @a auth_baton, making the data accessible to all providers. @a name and @a value will NOT be duplicated into the auth_baton’s pool. To delete a run-time parameter, pass NULL for @a value.