perf(pack): reduce number of 'opt/' directory computations

runtime/lua/vim/pack.lua

@@ -270,10 +270,11 @@ end
 --- @field info vim.pack.PlugInfo Gathered information about plugin.
 
 --- @param spec string|vim.pack.Spec
+--- @param plug_dir string?
 --- @return vim.pack.Plug
-local function new_plug(spec)
+local function new_plug(spec, plug_dir)
   local spec_resolved = normalize_spec(spec)
-  local path = vim.fs.joinpath(get_plug_dir(), spec_resolved.name)
+  local path = vim.fs.joinpath(plug_dir or get_plug_dir(), spec_resolved.name)
   local info = { err = '', installed = uv.fs_stat(path) ~= nil }
   return { spec = spec_resolved, path = path, info = info }
 end
@@ -324,6 +325,7 @@ end
 --- @return vim.pack.Plug[]
 local function plug_list_from_names(names)
   local all_plugins = M.get()
+  local plug_dir = get_plug_dir()
   local plugs = {} --- @type vim.pack.Plug[]
   local used_names = {} --- @type table<string,boolean>
   -- Preserve plugin order; might be important during checkout or event trigger
@@ -334,7 +336,7 @@ local function plug_list_from_names(names)
     -- TODO(echasnovski): Consider changing this if/when there is lockfile.
     --- @cast names string[]
     if (not names and p_data.active) or vim.tbl_contains(names or {}, p_data.spec.name) then
-      plugs[#plugs + 1] = new_plug(p_data.spec)
+      plugs[#plugs + 1] = new_plug(p_data.spec, plug_dir)
       used_names[p_data.spec.name] = true
     end
   end
@@ -712,8 +714,11 @@ function M.add(specs, opts)
   opts = vim.tbl_extend('force', { load = vim.v.vim_did_enter == 1, confirm = true }, opts or {})
   vim.validate('opts', opts, 'table')
 
-  --- @type vim.pack.Plug[]
-  local plugs = vim.tbl_map(new_plug, specs)
+  local plug_dir = get_plug_dir()
+  local plugs = {} --- @type vim.pack.Plug[]
+  for i = 1, #specs do
+    plugs[i] = new_plug(specs[i], plug_dir)
+  end
   plugs = normalize_plugs(plugs)
 
   -- Install