Command stack shows wrong relation member count

[GerdP]

What steps will reproduce the problem?

1. Load example.osm from #16006
2. Select a way named "Click this, then Ctrl-Alt-Shift-P"
3. Ctrl-Alt-Shift-P
4. Open the Command Stack window
5. Click on all + Symbols in the stack to expand the commands

What is the expected result?

The first "change relation" action should show
Change relation multipolygon ("park", 4 members) [id: 0]
because the relation had 4 members before step 3
The second "change relation" action should show
Change relation multipolygon ("park", 5 members) [id: 0]
because the relation had 5 members after the first change

What happens instead?

Both changes say
Change relation multipolygon ("park", 6 members) [id: 0]

Please provide any additional information below. Attach a screenshot if possible.

Build-Date:2018-12-23 10:15:27
Revision:14594
Is-Local-Build:true

Identification: JOSM/1.5 (14594 SVN en) Windows 10 64-Bit
OS Build number: Windows 10 Home 1803 (17134)
Memory Usage: 1504 MB / 5461 MB (1280 MB allocated, but free)
Java version: 1.8.0_191-b12, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: \Display0 1920x1080
Maximum Screen Size: 1920x1080
Dataset consistency test: No problems found

Plugins:
+ OpeningHoursEditor (34535)
+ apache-commons (34506)
+ buildings_tools (34724)
+ download_along (34503)
+ ejml (34389)
+ geotools (34513)
+ jaxb (34506)
+ jts (34524)
+ o5m (34405)
+ opendata (34698)
+ pbf (34576)
+ poly (34546)
+ reverter (34552)
+ utilsplugin2 (34790)

Last errors/warnings:
- W: Update plugins - org.openstreetmap.josm.plugins.PluginHandler$UpdatePluginsMessagePanel[,0,0,0x0,invalid,layout=java.awt.GridBagLayout,alignmentX=0.0,alignmentY=0.0,border=,flags=9,maximumSize=,minimumSize=,preferredSize=]
- W: No configuration settings found.  Using hardcoded default values for all pools.
- E: Invalid line in resource://data/validator/ignoretags.cfg : 'fire_hydrant:pressure' does not contain '='
- W: Cannot start IPv4 remotecontrol https server on port 8112: Keystore was tampered with, or password was incorrect
- W: Cannot start IPv6 remotecontrol https server on port 8112: Keystore was tampered with, or password was incorrect

[simon04]

To fix this, we'd have to persist org.openstreetmap.josm.command.ChangeCommand#getDescriptionText in the command constructor.

[GerdP]

Yes, and that would require more memory. Probably not important enough for that.