perf(plugin): de-duplicate dependencies, keys, ft, event and cmd

lua/lazy/core/plugin.lua

@@ -287,7 +287,7 @@ function Spec:merge(old, new)
   end
 
   if new.dependencies and old.dependencies then
-    vim.list_extend(new.dependencies, old.dependencies)
+    Util.extend(new.dependencies, old.dependencies)
   end
 
   new._.super = old
@@ -424,7 +424,7 @@ function M.values(plugin, prop, is_list)
   end
 
   values = type(values) == "table" and values or { values }
-  return is_list and vim.list_extend(ret, values) or Util.merge(ret, values)
+  return is_list and Util.extend(ret, values) or Util.merge(ret, values)
 end
 
 return M

lua/lazy/core/util.lua

@@ -222,6 +222,23 @@ function M.lsmod(modname, fn)
   end)
 end
 
+---@generic T
+---@param list T[]
+---@param add T[]
+---@return T[]
+function M.extend(list, add)
+  local idx = {}
+  for _, v in ipairs(list) do
+    idx[v] = v
+  end
+  for _, a in ipairs(add) do
+    if not idx[a] then
+      table.insert(list, a)
+    end
+  end
+  return list
+end
+
 ---@alias LazyNotifyOpts {lang?:string, title?:string, level?:number}
 
 ---@param msg string|string[]