Should not warn about "Deleted or moved objects" when using download along

[naoliv]

Open the attached example file, select any way, download along it (I am using 500 meters and 20 km² as parameters), select the other way and download along it too.

JOSM gives a warning about deleted or moved objects (although nothing has been modified):

Unless there is a reason that I can't see, probably multiple runs of Download along should not trigger a warning like this.

JOSM:

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2019-09-09 23:22:13 +0200 (Mon, 09 Sep 2019)
Revision:15343
Build-Date:2019-09-10 01:30:55
URL:https://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (15343 en) Linux Debian GNU/Linux bullseye/sid
Memory Usage: 306 MB / 2048 MB (112 MB allocated, but free)
Java version: 13+33-Debian-1, Debian, OpenJDK 64-Bit Server VM
Screen: :0.0 1920x1080
Maximum Screen Size: 1920x1080
Java ATK Wrapper package: libatk-wrapper-java:all-0.36.0-1
libcommons-compress-java: libcommons-compress-java:all-1.18-2
libcommons-logging-java: libcommons-logging-java:all-1.2-2
VM arguments: [-Dawt.useSystemAAFontSettings=gasp]
Program arguments: [--language=en]
Dataset consistency test: No problems found

Plugins:
+ EasyPresets (1537621333)
+ FastDraw (34977)
+ OpeningHoursEditor (34977)
+ SimplifyArea (34977)
+ apache-commons (34908)
+ buildings_tools (34982)
+ ejml (35049)
+ geojson (124)
+ geotools (34908)
+ http2 (35062)
+ jaxb (35014)
+ jogl (1.2.3)
+ jts (35064)
+ log4j (34908)
+ measurement (35051)
+ opendata (35102)
+ reverter (35084)
+ tageditor (34977)
+ tagging-preset-tester (34908)
+ todo (30306)
+ turnlanes-tagging (281)
+ turnrestrictions (34977)
+ undelete (34977)
+ utilsplugin2 (35098)
+ wikipedia (v1.1.1)

[Don-vip]

This code has been written in r2325 with the "update data" use case in mind (which was probably the only use case at the time). It checks that after having performed multiple downloads in several areas, all OSM objects already present are found in the downloaded data (otherwise it means someone has deleted the objects on server meanwhile). Code must check only objects present in the currently downloaded areas, not all downloaded areas from the current layer.

[Don-vip]

In 15353/josm:

fix #18118 - don't warn about potentially deleted objects when using download along several times