Indent multi-line values on replacement

Indent multi-line values when they replace a value in a
ConfigDocument.

config/src/main/java/com/typesafe/config/impl/ConfigNodeObject.java

@@ -69,7 +69,15 @@ final class ConfigNodeObject extends ConfigNodeComplexValue {
                 }
             } else if (key.equals(desiredPath)) {
                 seenNonMatching = true;
-                childrenCopy.set(i, node.replaceValue(value));
+                AbstractConfigNodeValue indentedValue;
+                AbstractConfigNode before = i - 1 > 0 ? childrenCopy.get(i - 1) : null;
+                if (value instanceof ConfigNodeComplexValue &&
+                        before instanceof ConfigNodeSingleToken &&
+                        Tokens.isIgnoredWhitespace(((ConfigNodeSingleToken) before).token()))
+                    indentedValue = ((ConfigNodeComplexValue) value).indentText(before);
+                else
+                    indentedValue = value;
+                childrenCopy.set(i, node.replaceValue(indentedValue));
                 valueCopy = null;
             } else if (desiredPath.startsWith(key)) {
                 seenNonMatching = true;

config/src/test/scala/com/typesafe/config/impl/ConfigDocumentTest.scala

@@ -413,4 +413,17 @@ class ConfigDocumentTest extends TestUtils {
         assertEquals("a { b {\n  c: d\n}, e : f }", configDocument.setValue("a.e", "f").render())
     }
 
+    @Test
+    def configDocumentIndentationReplacingWithMultiLineValue {
+        var origText = "a {\n  b {\n    c : 22\n  }\n}"
+        var configDocument = ConfigDocumentFactory.parseString(origText)
+
+        assertEquals("a {\n  b {\n    c : {\n      d:e\n    }\n  }\n}", configDocument.setValue("a.b.c", "{\n  d:e\n}").render())
+
+        origText = "a {\n  b {\n                f : 10\n    c : 22\n  }\n}"
+        configDocument = ConfigDocumentFactory.parseString(origText)
+
+        assertEquals("a {\n  b {\n                f : 10\n    c : {\n      d:e\n    }\n  }\n}", configDocument.setValue("a.b.c", "{\n  d:e\n}").render())
+    }
+
 }