feat(gen_help_html.lua): adapt to new parser

- adapt to parser changes from https://github.com/vigoux/tree-sitter-vimdoc/pull/16
- numerous other generator improvements

test/functional/helpers.lua

@@ -29,6 +29,7 @@ local module = {
 }
 
 local start_dir = lfs.currentdir()
+local runtime_set = 'set runtimepath^=./build/lib/nvim/'
 module.nvim_prog = (
   os.getenv('NVIM_PRG')
   or global_helpers.test_build_dir .. '/bin/nvim'
@@ -40,6 +41,8 @@ module.nvim_set = (
   ..' belloff= wildoptions-=pum joinspaces noshowcmd noruler nomore redrawdebug=invalid')
 module.nvim_argv = {
   module.nvim_prog, '-u', 'NONE', '-i', 'NONE',
+  -- XXX: find treesitter parsers.
+  '--cmd', runtime_set,
   '--cmd', module.nvim_set,
   '--cmd', 'mapclear',
   '--cmd', 'mapclear!',
@@ -345,14 +348,17 @@ end
 
 --  Removes Nvim startup args from `args` matching items in `args_rm`.
 --
---  "-u", "-i", "--cmd" are treated specially: their "values" are also removed.
+--  - Special case: "-u", "-i", "--cmd" are treated specially: their "values" are also removed.
+--  - Special case: "runtimepath" will remove only { '--cmd', 'set runtimepath^=…', }
+--
 --  Example:
 --      args={'--headless', '-u', 'NONE'}
 --      args_rm={'--cmd', '-u'}
 --  Result:
 --      {'--headless'}
 --
---  All cases are removed.
+--  All matching cases are removed.
+--
 --  Example:
 --      args={'--cmd', 'foo', '-N', '--cmd', 'bar'}
 --      args_rm={'--cmd', '-u'}
@@ -373,6 +379,9 @@ local function remove_args(args, args_rm)
       last = ''
     elseif tbl_contains(args_rm, arg) then
       last = arg
+    elseif arg == runtime_set and tbl_contains(args_rm, 'runtimepath') then
+      table.remove(new_args)  -- Remove the preceding "--cmd".
+      last = ''
     else
       table.insert(new_args, arg)
     end