added PushStateDispatcher for production and development to WebResourceServlet

scm-webapp/src/main/java/sonia/scm/PushStateDispatcherProvider.java

@@ -0,0 +1,28 @@
+package sonia.scm;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Strings;
+
+import javax.inject.Provider;
+
+/**
+ * Injection Provider for the {@link PushStateDispatcher}. The provider will return a {@link ProxyPushStateDispatcher}
+ * if the system property {@code PushStateDispatcherProvider#PROPERTY_TARGET} is set to a proxy target url, otherwise
+ * a {@link ForwardingPushStateDispatcher} is used.
+ *
+ * @since 2.0.0
+ */
+public class PushStateDispatcherProvider implements Provider<PushStateDispatcher> {
+
+  @VisibleForTesting
+  static final String PROPERTY_TARGET = "sonia.scm.ui.proxy";
+
+  @Override
+  public PushStateDispatcher get() {
+    String target = System.getProperty(PROPERTY_TARGET);
+    if (Strings.isNullOrEmpty(target)) {
+      return new ForwardingPushStateDispatcher();
+    }
+    return new ProxyPushStateDispatcher(target);
+  }
+}