Adapt 'Merge' button text to 'Merge layer' and 'Merge selection' actions

[nevw]

What steps will reproduce the problem?

1. Selecting Edit, 'merge layer' instead of an intended 'merge selected'
2. I have by mistake selected the 'merge layer' instead of 'merge selected' a couple of times and had to abort the session with much editing lost.

What is the expected result?

I would like an extra step added added to the 'Merge layer' button to warn if you really meant to merge the layer and that this command can't be undone. I suppose the text on the button would to be changed from 'Merge layer' to 'Merge layer...' too.

What happens instead?

I find the Edit, 'Merge layer' command on the main menu to be quite dangerous as there is no undo for the merge actions that I know of.
Recovering from such a mistake in 'Merge selected' is generally a simple task but recovering from 'Merge layer' is mostly a disaster as the layer is likely to be a large amount of data.

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

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2019-09-29 23:59:43 +0200 (Sun, 29 Sep 2019)
Build-Date:2019-09-29 22:01:37
Revision:15390
Relative:URL: ^/trunk

Identification: JOSM/1.5 (15390 en_AU) Mac OS X 10.14.6
OS Build number: Mac OS X 10.14.6 (18G95)
Memory Usage: 837 MB / 1820 MB (344 MB allocated, but free)
Java version: 1.8.0_221-b11, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: Display 69951636 2048x1152
Maximum Screen Size: 2048x1152
VM arguments: [-Djava.library.path=/private/var/folders/z5/0092mtt52c5ckgm0blz8xz1w0000gp/T/AppTranslocation/D030603F-EBCC-42DD-A170-865A984B7B2A/d/JOSM.app/Contents/MacOS, -DLibraryDirectory=${HOME}/Library, -DDocumentsDirectory=${HOME}/Documents, -DApplicationSupportDirectory=${HOME}/Library/Application Support, -DCachesDirectory=${HOME}/Library/Caches, -DApplicationDirectory=${HOME}/Applications, -DAutosavedInformationDirectory=${HOME}/Library/Autosave Information, -DDesktopDirectory=${HOME}/Desktop, -DDownloadsDirectory=${HOME}/Downloads, -DMoviesDirectory=${HOME}/Movies, -DMusicDirectory=${HOME}/Music, -DPicturesDirectory=${HOME}/Pictures, -DSharedPublicDirectory=${HOME}/Public, -DSystemLibraryDirectory=/Library, -DSystemApplicationSupportDirectory=/Library/Application Support, -DSystemCachesDirectory=/Library/Caches, -DSystemApplicationDirectory=/Applications, -DSystemUserDirectory=/Users, -DUserHome=${HOME}, -DSandboxEnabled=true, -DLaunchModifierFlags=0, -DLaunchModifierFlagCapsLock=false, -DLaunchModifierFlagShift=false, -DLaunchModifierFlagControl=false, -DLaunchModifierFlagOption=false, -DLaunchModifierFlagCommand=false, -DLaunchModifierFlagNumericPad=false, -DLaunchModifierFlagHelp=false, -DLaunchModifierFlagFunction=false, -Dapple.laf.useScreenMenuBar=true, -Dcom.apple.macos.use-file-dialog-packages=true, -Dcom.apple.macos.useScreenMenuBar=true, -Dcom.apple.mrj.application.apple.menu.about.name=JOSM, -Dcom.apple.smallTabs=true]

Plugins:
+ DirectUpload (35041)
+ FastDraw (34977)
+ ImproveWay (26)
+ InfoMode (34908)
+ Mapillary (1.5.19)
+ PicLayer (35104)
+ apache-commons (35092)
+ apache-http (34908)
+ conflation (0.6.4)
+ ejml (35122)
+ ext_tools (34988)
+ geojson (124)
+ geotools (35154)
+ graphview (34977)
+ jaxb (35014)
+ jna (34908)
+ jts (35122)
+ log4j (34908)
+ measurement (35051)
+ opendata (35156)
+ openvisible (34908)
+ pbf (35033)
+ pdfimport (34977)
+ reverter (35084)
+ rex (53)
+ routing (35039)
+ todo (30306)
+ turnrestrictions (34977)
+ utilsplugin2 (35098)

Tagging presets:
+ https://raw.githubusercontent.com/OpenNauticalChart/josm/master/Presets_Hafen.xml

Map paint styles:
- https://josm.openstreetmap.de/josmfile?page=Styles/Cycleways&zip=1
- https://github.com/bastik/mapcss-tools/raw/osm/mapnik2mapcss/osm-results/mapnik.zip
- https://josm.openstreetmap.de/josmfile?page=Styles/Maxspeed&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Noname&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Lane_and_Road_Attributes&zip=1
- https://github.com/igitov/forest-josm-style/archive/master.zip
- https://josm.openstreetmap.de/josmfile?page=Styles/LessObtrusiveNodes&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Coloured_Suburb&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/light_source&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/sac_scale&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Sidewalks&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Noname&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/DestinationSignRelation&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Enhanced_Lane_and_Road_Attributes&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Lane_features&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Lane_features_ryg&zip=1
- https://www.dropbox.com/s/qo3ai47fpv241jf/Styles_Fixme_and_Notes.zip?raw=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Fixme&zip=1
- /Volumes/Samsung SSD/JOSM/My MapPaint Styles/nevw_waterways
- https://raw.githubusercontent.com/OpenSeaMap/josm/master/INT1_Seamark.mapcss

Last errors/warnings:
- W: Invalid plugin main version '0.1.0' in plugin microdata_scraping
- E: Failed to locate image 'https://www.spatial.nsw.gov.au/__data/assets/file/0010/210520/favicon.ico'
- E: Failed to locate image 'https://www.spatial.nsw.gov.au/__data/assets/file/0010/210520/favicon.ico'
- W: No configuration settings found.  Using hardcoded default values for all pools.
- W: Region [TMS_BLOCK_v2] Resetting cache

[Don-vip]

Replying to nevw:

the text on the button would to be changed from 'Merge layer' to 'Merge layer...' too.

This is enough to avoid the confusion, and better than add another confirmation dialog that others may find annoying.

[Don-vip]

In 15450/josm:

fix #18216 - Adapt 'Merge' button text to 'Merge layer' and 'Merge selection' actions

[Don-vip]

In 15455/josm:

see #18219, see #18216 - update unit tests

[nevw]

I have added a 'Merge selection' button to the toolbar and use it from there. That is a good fix for me. Thanks, sorry for the noise.