If you need the data in a navigation app, (and not only in JOSM as in nevw's answer), the fastest solution I am aware of the live update functionality of OsmAnd. It updates every hour or so. Note that this is not a free service. Edit: I was told the the live update is free in the f-droid version of OsmAnd

If you need the data in a navigation app, (and not only in JOSM as in nevw's answer), the fastest solution I am aware of the live update functionality of OsmAnd. It updates every hour or so. Note that this is not a free service.