Reverting a changeset removes unmodified tags

[Cobra]

When reverting a changeset, the reverter plugin removes tags from some nodes.

1. open josm
2. revert changeset 15875373, downloading needed data, zoom to data (ignore conflicts)
3. undo, watch data, see some traffic lights and crossing symbols appear
4. Select one of these nodes, watch its tags
5. redo, then undo again and notice that all tags are being removed
6. Look at the history, e.g. ​http://osm.mapki.com/history/node.php?id=480761975 and see that this node's tags shouldn't be touched by this revert.

Again, this is severly damaging data and might be quite difficult to notice.

Might be related to #8676.

Build-Date: 2013-05-06 11:49:36
Revision: 5932
Is-Local-Build: true

Identification: JOSM/1.5 (5932 SVN en) Linux Ubuntu 11.04
Memory Usage: 221 MB / 3640 MB (86 MB allocated, but free)
Java version: 1.7.0_21, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
VM arguments: [-Xmx4G, -Dsun.java2d.opengl=false]
Dataset consistency test: No problems found

*snip*
Plugin: reverter (29561)
*snap*

[Cobra]

Also related: #8680, an issue with the history dialog uncovered when looking at this bug.

[Don-vip]

core problem caused by r5919.

[Don-vip]

In 5935/josm:

fix #8679, fix #8680 - correct handling of incomplete nodes without coordinates (for good)