How do I specify a war file I want to deploy in Gretty plugin?

I’m trying to use the Gretty plugin and finding it a hard slog - there just isn’t any documentation covering what seems like basic stuff.

So I’ve managed to get the current Gretty plugin (2.3.1) to load in the current Gradle (5.4.1) and the appRunWar task is now available. How do I tell it to use the WAR file that I just built in the war task? It looks like appRunWar is trying to build its own WAR file, and that’s not going to work - unless I need to specify the parameters that I already specified in the war task itself (which would be duplicated code)?

I have a Stack Overflow question open for this: