vim-patch:9.0.0346: :horizontal modifier not fully supported

Problem:    :horizontal modifier not fully supported.
Solution:   Also use :horizontal for completion and user commands.
            (closes vim/vim#11025)
d3de178e53

src/nvim/cmdexpand.c

@@ -1203,6 +1203,7 @@ static const char *set_context_by_cmdname(const char *cmd, cmdidx_T cmdidx, cons
   case CMD_folddoclosed:
   case CMD_folddoopen:
   case CMD_hide:
+  case CMD_horizontal:
   case CMD_keepalt:
   case CMD_keepjumps:
   case CMD_keepmarks:

src/nvim/ex_docmd.c

@@ -1757,6 +1757,7 @@ static bool skip_cmd(const exarg_T *eap)
     case CMD_filter:
     case CMD_help:
     case CMD_hide:
+    case CMD_horizontal:
     case CMD_ijump:
     case CMD_ilist:
     case CMD_isearch:

src/nvim/testdir/test_cmdline.vim

@@ -926,6 +926,10 @@ func Test_cmdline_complete_various()
   call feedkeys(":all abc\<C-A>\<C-B>\"\<CR>", 'xt')
   call assert_equal("\"all abc\<C-A>", @:)
 
+  " completion for :wincmd with :horizontal modifier
+  call feedkeys(":horizontal wincm\<C-A>\<C-B>\"\<CR>", 'xt')
+  call assert_equal("\"horizontal wincmd", @:)
+
   " completion for a command with a command modifier
   call feedkeys(":topleft new\<C-A>\<C-B>\"\<CR>", 'xt')
   call assert_equal("\"topleft new", @:)

src/nvim/testdir/test_usercommands.vim

@@ -101,6 +101,10 @@ function Test_cmdmods()
   call assert_equal('vertical', g:mods)
   vert MyCmd
   call assert_equal('vertical', g:mods)
+  horizontal MyCmd
+  call assert_equal('horizontal', g:mods)
+  hor MyCmd
+  call assert_equal('horizontal', g:mods)
 
   aboveleft belowright botright browse confirm hide keepalt keepjumps
 	      \ keepmarks keeppatterns lockmarks noautocmd noswapfile silent

src/nvim/usercmd.c

@@ -1247,6 +1247,10 @@ size_t add_win_cmd_modifers(char *buf, const cmdmod_T *cmod, bool *multi_mods)
   if (cmod->cmod_split & WSP_VERT) {
     result += add_cmd_modifier(buf, "vertical", multi_mods);
   }
+  // :horizontal
+  if (cmod->cmod_split & WSP_HOR) {
+    result += add_cmd_modifier(buf, "horizontal", multi_mods);
+  }
   return result;
 }