Fix ChangePropertyKey whitespace quirks when moving subproperties (#7283)

Fixes #2608

Author: timtebeek

rewrite-yaml/src/main/java/org/openrewrite/yaml/ChangePropertyKey.java

@@ -350,7 +350,8 @@ public Yaml.Mapping visitMapping(Yaml.Mapping mapping, P p) {
             }
 
             if (entries.size() == 1) {
-                entries = ListUtils.map(entries, e -> e.withPrefix(""));
+                String firstEntryPrefix = m.getEntries().get(0).getPrefix();
+                entries = ListUtils.map(entries, e -> e.withPrefix(firstEntryPrefix));
             }
 
             if (changed) {

rewrite-yaml/src/test/java/org/openrewrite/yaml/ChangePropertyKeyTest.java

@@ -51,6 +51,53 @@ void singleEntry() {
         );
     }
 
+    @Issue("https://github.com/openrewrite/rewrite/issues/2608")
+    @Test
+    void moveSubpropertyOut() {
+        rewriteRun(
+          spec -> spec.recipe(new ChangePropertyKey("foo.bar", "bar", null, null, null)),
+          yaml(
+            """
+              foo:
+                bar:
+                  prop: val
+                other: other-val
+              """,
+            """
+              foo:
+                other: other-val
+              bar:
+                prop: val
+              """
+          )
+        );
+    }
+
+    @Issue("https://github.com/openrewrite/rewrite/issues/2608")
+    @Test
+    void multiDocument() {
+        rewriteRun(
+          spec -> spec.recipe(new ChangePropertyKey("foo.bar", "bar", null, null, null)),
+          yaml(
+            """
+              a: b
+              ---
+              foo:
+                bar:
+                  prop: val
+              other: other-val
+              """,
+            """
+              a: b
+              ---
+              other: other-val
+              bar:
+                prop: val
+              """
+          )
+        );
+    }
+
     @Issue("https://github.com/openrewrite/rewrite/issues/1873")
     @Test
     void shorterNewKeyWithIndentedConfig() {