vim-patch:8.2.0841: 'verbose' value 16 causes duplicate output

Problem:    'verbose' value 16 causes duplicate output.
Solution:   Combine levels 15 and 16 into one message. (Christian Brabandt,
            closes vim/vim#6153)
823654bc06

test/functional/ui/cmdline_spec.lua

@@ -3,6 +3,7 @@ local Screen = require('test.functional.ui.screen')
 local clear, feed = helpers.clear, helpers.feed
 local source = helpers.source
 local command = helpers.command
+local feed_command = helpers.feed_command
 
 local function new_screen(opt)
   local screen = Screen.new(25, 5)
@@ -842,3 +843,34 @@ describe('cmdline redraw', function()
     ]], unchanged=true}
   end)
 end)
+
+describe('cmdline', function()
+  before_each(function()
+    clear()
+  end)
+
+  it('prints every executed Ex command if verbose >= 16', function()
+    local screen = Screen.new(50, 12)
+    screen:attach()
+    source([[
+      command DoSomething echo 'hello' |set ts=4 |let v = '123' |echo v
+      call feedkeys("\r", 't') " for the hit-enter prompt
+      set verbose=20
+    ]])
+    feed_command('DoSomething')
+    screen:expect([[
+                                                        |
+      ~                                                 |
+                                                        |
+      Executing: DoSomething                            |
+      Executing: echo 'hello' |set ts=4 |let v = '123' ||
+      echo v                                            |
+      hello                                             |
+      Executing: set ts=4 |let v = '123' |echo v        |
+      Executing: let v = '123' |echo v                  |
+      Executing: echo v                                 |
+      123                                               |
+      Press ENTER or type command to continue^           |
+    ]])
+  end)
+end)