Improve error message for malformed edits

PiperOrigin-RevId: 479639885

Author: amalloy

core/src/main/java/com/google/googlejavaformat/java/StringWrapper.java

@@ -96,7 +96,9 @@ static String wrap(final int columnLimit, String input, Formatter formatter)
       if (!expected.equals(actual)) {
         throw new FormatterException(
             String.format(
-                "Something has gone terribly wrong. Please file a bug: "
+                "Something has gone terribly wrong. We planned to make the below formatting change,"
+                    + " but have aborted because it would unexpectedly change the AST.\n"
+                    + "Please file a bug: "
                     + "https://github.com/google/google-java-format/issues/new"
                     + "\n\n=== Actual: ===\n%s\n=== Expected: ===\n%s\n",
                 actual, expected));