vim-patch:9.1.1608: No command-line completion for :unsilent {command}

Problem:  No command-line completion for :unsilent {command}.
Solution: Add missing command arg completion (Doug Kearns).
          (author)

Add completion tests for all command modifiers.

closes: vim/vim#17524

126731c8fd

Co-authored-by: Doug Kearns <dougkearns@gmail.com>
(cherry picked from commit fe42c81f2e)

src/nvim/cmdexpand.c

@@ -1887,6 +1887,7 @@ static const char *set_context_by_cmdname(const char *cmd, cmdidx_T cmdidx, expa
   case CMD_tab:
   case CMD_tabdo:
   case CMD_topleft:
+  case CMD_unsilent:
   case CMD_verbose:
   case CMD_vertical:
   case CMD_windo:

test/old/testdir/test_cmdmods.vim

@@ -1,5 +1,23 @@
 " Test for all command modifiers in
 
+let s:luaeval_cmdmods =<< trim END
+  vim.iter(loadfile('../../../src/nvim/ex_cmds.lua')()):map(function(cmd)
+    if cmd.func == 'ex_wrongmodifier' or cmd.command == 'hide' then
+      return cmd.command
+    else
+      return nil
+    end
+  end):totable()
+END
+let s:cmdmods = []
+
+func s:get_cmdmods()
+  if empty(s:cmdmods)
+    let s:cmdmods = luaeval(s:luaeval_cmdmods->join("\n"))
+  endif
+  return s:cmdmods
+endfunc
+
 func Test_keep_cmdmods_names()
   call assert_equal('k', fullcommand(':k'))
   call assert_equal('k', fullcommand(':ke'))
@@ -29,10 +47,13 @@ func Test_keep_cmdmods_names()
 endfunc
 
 func Test_cmdmod_completion()
-  call assert_equal('edit', getcompletion('keepalt ed',      'cmdline')[0])
-  call assert_equal('edit', getcompletion('keepjumps ed',    'cmdline')[0])
-  call assert_equal('edit', getcompletion('keepmarks ed',    'cmdline')[0])
-  call assert_equal('edit', getcompletion('keeppatterns ed', 'cmdline')[0])
+  for mod in s:get_cmdmods()
+    let cmd = $'{mod} ed'
+    if mod == 'filter'
+      let cmd = $'{mod} /pattern/ ed'
+    endif
+    call assert_equal('edit', getcompletion(cmd, 'cmdline')[0])
+  endfor
 endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab