test: clear(): remove opts.headless parameter

Callers can instead specify `args_rm={'--headless'}`.

TODO: should `nvim_argv` have "--headless" by default? Need to inspect
      some uses of spawn(nvim_argv) ...

test/functional/helpers.lua

@@ -394,17 +394,16 @@ end
 --                removed, e.g. args_rm={'--cmd'} removes all cases of "--cmd"
 --                (and its value) from the default set.
 --    env:        Map: Defines the environment of the new session.
---    headless:   Boolean (default=true): Append --headless arg.
 --
 -- Example:
 --    clear('-e')
 --    clear{args={'-e'}, args_rm={'-i'}, env={TERM=term}}
 local function clear(...)
   local args = {unpack(nvim_argv)}
+  table.insert(args, '--headless')
   local new_args
   local env = nil
   local opts = select(1, ...)
-  local headless = true
   if type(opts) == 'table' then
     args = remove_args(args, opts.args_rm)
     if opts.env then
@@ -432,15 +431,9 @@ local function clear(...)
       end
     end
     new_args = opts.args or {}
-    if opts.headless == false then
-      headless = false
-    end
   else
     new_args = {...}
   end
-  if headless then
-    table.insert(args, '--headless')
-  end
   for _, arg in ipairs(new_args) do
     table.insert(args, arg)
   end

test/functional/ui/embed_spec.lua

@@ -8,7 +8,7 @@ local clear = helpers.clear
 local function test_embed(ext_linegrid)
   local screen
   local function startup(...)
-    clear{headless=false, args={...}}
+    clear{args_rm={'--headless'}, args={...}}
 
     -- attach immediately after startup, for early UI
     screen = Screen.new(60, 8)

test/functional/ui/messages_spec.lua

@@ -529,7 +529,7 @@ describe('ui/ext_messages', function()
   local screen
 
   before_each(function()
-    clear{headless=false, args={"--cmd", "set shortmess-=I"}}
+    clear{args_rm={'--headless'}, args={"--cmd", "set shortmess-=I"}}
     screen = Screen.new(80, 24)
     screen:attach({rgb=true, ext_messages=true, ext_popupmenu=true})
     screen:set_default_attr_ids({

test/functional/ui/multigrid_spec.lua

@@ -11,7 +11,7 @@ describe('ext_multigrid', function()
   local screen
 
   before_each(function()
-    clear{headless=false, args={'--cmd', 'set laststatus=2'}}
+    clear{args_rm={'--headless'}, args={'--cmd', 'set laststatus=2'}}
     screen = Screen.new(53,14)
     screen:attach({ext_multigrid=true})
     screen:set_default_attr_ids({

test/functional/ui/options_spec.lua

@@ -115,7 +115,8 @@ describe('ui receives option updates', function()
   end)
 
   local function startup_test(headless)
-    local expected = reset(nil,{headless=headless,args={'--cmd', 'set guifont=Comic\\ Sans\\ 12'}})
+    local expected = reset(nil, {args_rm=(headless and {} or {'--headless'}),
+                                 args={'--cmd', 'set guifont=Comic\\ Sans\\ 12'}})
     expected.guifont = "Comic Sans 12"
     screen:expect(function()
       eq(expected, screen.options)