Add a test that illustrates a problem with +4 indentation for block tags in Markdown Javadoc comments.

core/src/test/java/com/google/googlejavaformat/java/JavadocFormattingTest.java

@@ -1965,6 +1965,38 @@ class Test {}
     doFormatTest(input, expected);
   }
 
+  @Test
+  public void markdownBlockTagContinuationLines() {
+    assume().that(MARKDOWN_JAVADOC_SUPPORTED).isTrue();
+    String input =
+"""
+/// Something something something.
+///
+/// @param foo a parameter with a long description that will need to be wrapped onto multiple
+/// lines, with each line being indented by the default amount for continuation
+/// lines in a block tag.
+///
+/// There is even a second paragraph which illustrates why the indentation should be +2
+/// rather than +4.
+record Test(String foo) {}
+""";
+    // TODO(b/537488642): continuation lines should be +2 to avoid the bug here.
+    // The four-space indentation leads to the second paragraph being interpreted as a code block.
+    String expected =
+"""
+/// Something something something.
+///
+/// @param foo a parameter with a long description that will need to be wrapped onto multiple lines,
+///     with each line being indented by the default amount for continuation lines in a block tag.
+///
+///     There is even a second paragraph which illustrates why the indentation should be +2 rather
+///     than +4.
+record Test(String foo) {}
+""";
+
+    doFormatTest(input, expected);
+  }
+
   @Test
   public void markdownLinkReferenceDefinitions() {
     assume().that(MARKDOWN_JAVADOC_SUPPORTED).isTrue();