patch 8.2.0275: some Ex code not covered by tests

Problem:    Some Ex code not covered by tests.
Solution:   Add test cases. (Yegappan Lakshmanan, closes #5659)
diff --git a/src/testdir/test_arglist.vim b/src/testdir/test_arglist.vim
index 9513ad3..af90ddc 100644
--- a/src/testdir/test_arglist.vim
+++ b/src/testdir/test_arglist.vim
@@ -519,6 +519,20 @@
   call term_sendkeys(buf, ":quit\n")
   call WaitForAssert({-> assert_match('^E173:', term_getline(buf, 6))})
   call StopVimInTerminal(buf)
+
+  " Try :confirm quit with unedited files in arglist
+  let buf = RunVimInTerminal('', {'rows': 6})
+  call term_sendkeys(buf, ":set nomore\n")
+  call term_sendkeys(buf, ":args a b c\n")
+  call term_sendkeys(buf, ":confirm quit\n")
+  call WaitForAssert({-> assert_match('^\[Y\]es, (N)o: *$',
+        \ term_getline(buf, 6))})
+  call term_sendkeys(buf, "N")
+  call term_sendkeys(buf, ":confirm quit\n")
+  call WaitForAssert({-> assert_match('^\[Y\]es, (N)o: *$',
+        \ term_getline(buf, 6))})
+  call term_sendkeys(buf, "Y")
+  call StopVimInTerminal(buf)
 endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab