Monitor config additional locations for hot deployment.

(cherry picked from commit d3d70ac)

core/deployment/src/main/java/io/quarkus/deployment/steps/DevModeBuildStep.java

@@ -7,17 +7,19 @@
 
 import io.quarkus.deployment.annotations.BuildStep;
 import io.quarkus.deployment.builditem.HotDeploymentWatchedFileBuildItem;
+import io.quarkus.runtime.ConfigConfig;
 import io.quarkus.runtime.LiveReloadConfig;
 
 class DevModeBuildStep {
 
     @BuildStep
-    List<HotDeploymentWatchedFileBuildItem> watchChanges(LiveReloadConfig config) {
+    List<HotDeploymentWatchedFileBuildItem> watchChanges(ConfigConfig config, LiveReloadConfig liveReloadConfig) {
         List<String> names = new ArrayList<>();
         names.add("META-INF/microprofile-config.properties");
         names.add("application.properties");
         names.add(Paths.get(".env").toAbsolutePath().toString());
-        config.watchedResources.ifPresent(names::addAll);
+        config.locations.ifPresent(names::addAll);
+        liveReloadConfig.watchedResources.ifPresent(names::addAll);
         return names.stream().map(HotDeploymentWatchedFileBuildItem::new).collect(Collectors.toList());
     }
 }

core/runtime/src/main/java/io/quarkus/runtime/ConfigConfig.java

@@ -1,5 +1,6 @@
 package io.quarkus.runtime;
 
+import java.util.List;
 import java.util.Optional;
 
 import io.quarkus.runtime.annotations.ConfigItem;
@@ -19,7 +20,7 @@ public class ConfigConfig {
      * separated by a comma and each must represent a valid {@link java.net.URI}.
      */
     @ConfigItem(name = "config.locations")
-    public Optional<String> locations;
+    public Optional<List<String>> locations;
 
     /**
      * Accepts a single configuration profile name. If a configuration property cannot be found in the current active

core/test-extension/deployment/src/test/java/io/quarkus/extest/AdditionalLocationsTest.java

@@ -0,0 +1,66 @@
+package io.quarkus.extest;
+
+import static org.hamcrest.core.Is.is;
+
+import javax.enterprise.context.ApplicationScoped;
+import javax.enterprise.event.Observes;
+import javax.inject.Inject;
+
+import org.eclipse.microprofile.config.Config;
+import org.jboss.shrinkwrap.api.ShrinkWrap;
+import org.jboss.shrinkwrap.api.asset.StringAsset;
+import org.jboss.shrinkwrap.api.spec.JavaArchive;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import io.quarkus.runtime.StartupEvent;
+import io.quarkus.test.QuarkusDevModeTest;
+import io.restassured.RestAssured;
+import io.restassured.filter.log.RequestLoggingFilter;
+import io.restassured.filter.log.ResponseLoggingFilter;
+import io.vertx.ext.web.Router;
+
+public class AdditionalLocationsTest {
+    @RegisterExtension
+    static final QuarkusDevModeTest TEST = new QuarkusDevModeTest()
+            .setArchiveProducer(() -> ShrinkWrap.create(JavaArchive.class)
+                    .addClasses(DevBean.class)
+                    .addAsResource(new StringAsset("quarkus.config.locations=additional.properties\n"),
+                            "application.properties")
+                    .addAsResource(new StringAsset("additional.property=1234\n"), "additional.properties"));
+
+    @BeforeAll
+    static void beforeAll() {
+        RestAssured.filters(new RequestLoggingFilter(), new ResponseLoggingFilter());
+    }
+
+    @Test
+    void additionalLocations() {
+        // A combination of QuarkusUnitTest and QuarkusProdModeTest tests ordering may mess with the port leaving it in
+        // 8081 and QuarkusDevModeTest does not changes to the right port.
+        RestAssured.port = -1;
+
+        RestAssured.when().get("/config").then()
+                .statusCode(200)
+                .body(is("1234"));
+
+        TEST.modifyResourceFile("additional.properties", s -> "additional.property=5678\n");
+
+        RestAssured.when().get("/config").then()
+                .statusCode(200)
+                .body(is("5678"));
+    }
+
+    @ApplicationScoped
+    public static class DevBean {
+        @Inject
+        Router router;
+        @Inject
+        Config config;
+
+        public void register(@Observes StartupEvent ev) {
+            router.get("/config").handler(rc -> rc.response().end(config.getValue("additional.property", String.class)));
+        }
+    }
+}