patch 8.2.0308: 'showbreak' does not work for a very long line

Problem:    'showbreak' does not work for a very long line. (John Little)
Solution:   Check whether 'briopt' contains "sbr". (Ken Takata, closes #5523,
            closes #5684)
diff --git a/src/testdir/test_breakindent.vim b/src/testdir/test_breakindent.vim
index 6e4e090..ad4ae1d 100644
--- a/src/testdir/test_breakindent.vim
+++ b/src/testdir/test_breakindent.vim
@@ -682,5 +682,15 @@
 	\ "> aaaaaaaaaaaaaaaaaa",
 	\ ]
   call s:compare_lines(expect, lines)
+
+  setl breakindent briopt=min:18 sbr=>
+  norm! 5gj
+  let lines = s:screen_lines(1, 20)
+  let expect = [
+	\ ">aaaaaaaaaaaaaaaaaaa",
+	\ ">aaaaaaaaaaaaaaaaaaa",
+	\ ">aaaaaaaaaaaaaaaaaaa",
+	\ ]
+  call s:compare_lines(expect, lines)
   call s:close_windows('set breakindent& briopt& sbr&')
 endfunc