Added @IgnoreParameter meta annotation

retrofit/src/main/java/retrofit2/IgnoreParameter.java

@@ -0,0 +1,19 @@
+package retrofit2;
+
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import static java.lang.annotation.ElementType.TYPE;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+/**
+ * Use this meta-annotation on an annotation you want to use on a service method parameter to cause
+ * retrofit to ignore the parameter when processing a request.
+ */
+@Documented
+@Target(TYPE)
+@Retention(RUNTIME)
+public @interface IgnoreParameter {
+}

retrofit/src/main/java/retrofit2/ParameterHandler.java

@@ -446,4 +446,13 @@ void apply(RequestBuilder builder, @Nullable T value) {
       builder.addTag(cls, value);
     }
   }
+
+  static final class NoOp<T> extends ParameterHandler<T> {
+
+    @Override
+    void apply(RequestBuilder builder, @org.jetbrains.annotations.Nullable T value) throws IOException {
+      // do nothing
+    }
+  }
+
 }

retrofit/src/main/java/retrofit2/RequestFactory.java

@@ -803,9 +803,15 @@ private ParameterHandler<?> parseParameterAnnotation(
         }
 
         return new ParameterHandler.Tag<>(tagType);
+      } else if (shouldIgnoreParameter(annotation)) {
+        return new ParameterHandler.NoOp<>();
       }
 
-      return null; // Not a Retrofit annotation.
+      return null; // No ParameterHandler for annotation.
+    }
+
+    private boolean shouldIgnoreParameter(Annotation annotation){
+      return annotation.getClass().isAnnotationPresent(IgnoreParameter.class);
     }
 
     private void validateResolvableType(int p, Type type) {