// mergeSettings reads the relation settings node for the unit with the
// supplied id, and sets a value in the Changed field keyed on the unit's
// name. It returns the mgo/txn revision number of the settings node.
func (w *relationUnitsWatcher) mergeSettings(changes *params.RelationUnitsChange, key string) (int64, error) {
node, err := readSettings(w.st, key)
if err != nil {
return -1, err
}
name := (&relationScopeDoc{key}).unitName()
settings := params.UnitSettings{Version: node.txnRevno}
if changes.Changed == nil {
changes.Changed = map[string]params.UnitSettings{name: settings}
} else {
changes.Changed[name] = settings
}
return node.txnRevno, nil
}
