[clang] [clang-format] Introduce "ReflowComments: IndentOnly" to re-indent comments without breaking internal structure (think Doxygen). (PR #96804)

[Owen Pan via cfe-commits]

================
@@ -493,9 +493,36 @@ TEST_F(FormatTestComments, AlignsBlockComments) {
 
 TEST_F(FormatTestComments, CommentReflowingCanBeTurnedOff) {
   FormatStyle Style = getLLVMStyleWithColumns(20);
-  Style.ReflowComments = false;
-  verifyFormat("// aaaaaaaaa aaaaaaaaaa aaaaaaaaaa", Style);
-  verifyFormat("/* aaaaaaaaa aaaaaaaaaa aaaaaaaaaa */", Style);
+  Style.ReflowComments = FormatStyle::RCS_Never;
+  verifyNoChange("// aaaaaaaaa aaaaaaaaaa aaaaaaaaaa", Style);
+  verifyNoChange("/* aaaaaaaaa aaaaaaaaaa aaaaaaaaaa */", Style);
+  verifyNoChange("/* aaaaaaaaa aaaaaaaaaa aaaaaaaaaa\n"
+                 "aaaaaaaaa*/",
+                 Style);
+  verifyNoChange("/* aaaaaaaaa aaaaaaaaaa aaaaaaaaaa\n"
+                 "    aaaaaaaaa*/",
+                 Style);
+  verifyNoChange("/* aaaaaaaaa aaaaaaaaaa aaaaaaaaaa\n"
+                 " *    aaaaaaaaa*/",
+                 Style);
+}
+
+TEST_F(FormatTestComments, CommentReflowingCanApplyOnlyToIndents) {
+  FormatStyle Style = getLLVMStyleWithColumns(20);
+  Style.ReflowComments = FormatStyle::RCS_IndentOnly;
+  verifyNoChange("// aaaaaaaaa aaaaaaaaaa aaaaaaaaaa", Style);
+  verifyNoChange("/* aaaaaaaaa aaaaaaaaaa aaaaaaaaaa */", Style);
----------------
owenca wrote:

```suggestion
  verifyFormat("// aaaaaaaaa aaaaaaaaaa aaaaaaaaaa", Style);
  verifyFormat("/* aaaaaaaaa aaaaaaaaaa aaaaaaaaaa */", Style);
```

https://github.com/llvm/llvm-project/pull/96804