JoinLinesHandler: Add symmetric spacing to block comments

GitOrigin-RevId: f83830b995a9b7e33a8000d00838aa6fde5aee8d

java/java-tests/testData/codeInsight/joinLines/ConvertComment2_after.java

@@ -1,6 +1,6 @@
 class A {
   // IDEA-138747
   void myMethod() {
-    /* int myOldCodeCommentedOut;    * /    with an old comment (only closure)*/int somecode;
+    /* int myOldCodeCommentedOut;    * /    with an old comment (only closure) */int somecode;
   }
 }

java/java-tests/testData/codeInsight/joinLines/ConvertFinalLineComment3_after.java

@@ -1,4 +1,4 @@
 class A {
-  /* foo*/ int x;
+  /* foo */ int x;
 
 }

platform/lang-impl/src/com/intellij/codeInsight/editorActions/JoinLinesHandler.java

@@ -408,6 +408,10 @@ public class JoinLinesHandler extends EditorActionHandler.ForEachCaret {
           String fixedSuffix = suffix.charAt(0)+" "+suffix.substring(1);
           commentText = commentText.replace(suffix, fixedSuffix);
         }
+        if (commentText.startsWith(" ") && !commentText.endsWith(" ")) {
+          // "// foo" should be translated to "/* foo */" not "/* foo*/"
+          commentText += " ";
+        }
         try {
           Project project = commentElement.getProject();
           PsiParserFacade parserFacade = PsiParserFacade.SERVICE.getInstance(project);

plugins/kotlin/idea/tests/testData/joinLines/addSemicolon/FunctionCallsAndAComment.kt.after

@@ -1,3 +1,3 @@
 fun foo() {
-    println(); /* A very important comment*/<caret> println()
+    println(); /* A very important comment */<caret> println()
 }

plugins/kotlin/idea/tests/testData/joinLines/removeTrailingComma/destructuringDeclarationsInLambda.kt.after

@@ -1,3 +1,3 @@
 fun a() {
-    val a = { (a, b /* awd*//**/<caret>), c, -> }
+    val a = { (a, b /* awd *//**/<caret>), c, -> }
 }