Fix NanoLimbo port not applying to an existing settings.yml (#4201)

tests/setuponlytests/nanolimbo-existing-settings/docker-compose.yml

@@ -0,0 +1,23 @@
+services:
+  # copies seed/ into /data before mc starts, so the NanoLimbo setup takes its
+  # "settings.yml already exists" path instead of writing the template
+  seed:
+    restart: "no"
+    image: ${IMAGE_TO_TEST:-itzg/minecraft-server}
+    entrypoint: ["bash", "-c", "cp /seed/settings.yml /data/ && chown -R 1000:1000 /data"]
+    volumes:
+      - ./seed:/seed
+      - ./data:/data
+
+  mc:
+    restart: "no"
+    image: ${IMAGE_TO_TEST:-itzg/minecraft-server}
+    depends_on:
+      seed:
+        condition: service_completed_successfully
+    environment:
+      EULA: "TRUE"
+      TYPE: NANOLIMBO
+      SERVER_PORT: "25599"
+    volumes:
+      - ./data:/data

tests/setuponlytests/nanolimbo-existing-settings/seed/settings.yml

@@ -0,0 +1,4 @@
+bind:
+  ip: '0.0.0.0'
+  port: 25565
+maxPlayers: 100

tests/setuponlytests/nanolimbo-existing-settings/verify.sh

@@ -0,0 +1,4 @@
+set -e
+# SERVER_PORT must have been applied to the settings.yml that was already there
+port=$(mc-image-helper yaml-path --file /data/settings.yml .bind.port)
+[ "$port" = 25599 ] || { echo "expected bind.port 25599 but was '$port'"; exit 1; }