[#3164] Missing formatting when rendering formatted MERGE statement's SET clause

jOOQ-test/src/org/jooq/test/_/testcases/InsertUpdateTests.java

@@ -1064,6 +1064,7 @@ extends BaseTest<A, AP, B, S, B2S, BS, L, X, DATE, BOOL, D, T, U, UU, I, IPK, T7
                 .on(TAuthor_LAST_NAME().equal(l))
                 .whenMatchedThenUpdate()
                 .set(TAuthor_FIRST_NAME(), "James")
+                .set(TAuthor_LAST_NAME(), "Dean")
                 .whenNotMatchedThenInsert()
                 .set(TAuthor_ID(), 3)
                 .set(TAuthor_FIRST_NAME(), f)

jOOQ/src/main/java/org/jooq/impl/MergeImpl.java

@@ -1164,7 +1164,10 @@ implements
         if (matchedUpdate != null) {
             context.formatSeparator()
                    .keyword("when matched then update set").sql(" ")
-                   .visit(matchedUpdate);
+                   .formatIndentStart()
+                   .formatSeparator()
+                   .visit(matchedUpdate)
+                   .formatIndentEnd();
         }
 
         context.end(MERGE_SET)