ci: do not mess with runtimepath

tests/init.lua

@@ -1,15 +1,19 @@
 local M = {}
 
+---@param root string?
+---@return string
 function M.root(root)
   local f = debug.getinfo(1, "S").source:sub(2)
-  return vim.fn.fnamemodify(f, ":p:h:h") .. "/" .. (root or "")
+  f = vim.fn.fnamemodify(f, ":p:h:h")
+  if root then f = f .. "/" .. root end
+  return f
 end
 
 ---@param plugin string
 function M.load(plugin)
   local name = plugin:match(".*/(.*)")
   local package_root = M.root(".tests/site/pack/deps/start/")
-  if not vim.loop.fs_stat(package_root .. name) then
+  if not vim.uv.fs_stat(package_root .. name) then
     print("Installing " .. plugin)
     vim.fn.mkdir(package_root, "p")
     vim.fn.system({
@@ -23,7 +27,6 @@ function M.load(plugin)
 end
 
 function M.setup()
-  vim.cmd([[set runtimepath=$VIMRUNTIME]])
   vim.opt.runtimepath:append(M.root())
   vim.opt.packpath = { M.root(".tests/site") }
   M.load("nvim-lua/plenary.nvim")