josm: add update script

Tested by reverting 7e2e65497c temporarily
and running the script. I got the same diff, and the output was cached,
so I'm pretty sure this works.

pkgs/by-name/jo/josm/package.nix

@@ -63,6 +63,11 @@ stdenv.mkDerivation {
           --prefix _JAVA_OPTIONS : "-Dawt.useSystemAAFontSettings=on"
       '';
 
+  passthru = {
+    inherit srcs;
+    updateScript = ./update.sh;
+  };
+
   meta = {
     description = "Extensible editor for OpenStreetMap";
     homepage = "https://josm.openstreetmap.de/";

pkgs/by-name/jo/josm/update.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash -p curl nurl pup common-updater-scripts
+
+# partially taken from jitsi-meet/update.sh, as they both scrape an apt repo.
+
+set -euo pipefail
+
+version="$(curl https://josm.openstreetmap.de/apt/pool/universe/j/josm/ |
+  pup 'a[href] text{}' |
+  sed -nr 's/josm_[0-9]+.[0-9]+.svn([0-9]+)_all.deb/\1/p' |
+  sort -n |
+  tail -n1)"
+
+pkgHash="$(nurl -H https://github.com/JOSM/josm "$version-tested")"
+
+update-source-version josm "$version" --source-key=srcs.jar
+update-source-version josm "$version" --ignore-same-version --source-key=srcs.macosx
+update-source-version josm "$version" "$pkgHash" --ignore-same-version --source-key=srcs.pkg