Replace *just with pad_* calls and optimize around

lib/elixir/lib/io/ansi/docs.ex

@@ -43,7 +43,7 @@ defmodule IO.ANSI.Docs do
     options = Keyword.merge(default_options, options)
     width   = options[:width]
     padding = div(width + String.length(heading), 2)
-    heading = heading |> String.rjust(padding) |> String.ljust(width)
+    heading = heading |> String.pad_leading(padding) |> String.pad_trailing(width)
     write(:doc_title, heading, options)
     newline_after_block
   end

lib/elixir/lib/kernel/parallel_compiler.ex

@@ -251,7 +251,7 @@ defmodule Kernel.ParallelCompiler do
       |> Enum.max
 
     for {file, mod} <- deadlock do
-      IO.puts "  " <> String.rjust(file, max) <> " => " <> inspect(mod)
+      IO.puts ["  ", String.pad_leading(file, max), " => " | inspect(mod)]
     end
 
     IO.puts ""

lib/ex_unit/lib/ex_unit/formatter.ex

@@ -194,7 +194,7 @@ defmodule ExUnit.Formatter do
   defp format_label(:note, _formatter), do: ""
 
   defp format_label(label, formatter) do
-    formatter.(:extra_info, String.ljust("#{label}:", byte_size(@label_padding)))
+    formatter.(:extra_info, String.pad_trailing("#{label}:", byte_size(@label_padding)))
   end
 
   defp format_banner(value, formatter) do

lib/iex/lib/iex.ex

@@ -335,7 +335,7 @@ defmodule IEx do
       nil ->
         string
       ansi ->
-        IO.iodata_to_binary([IO.ANSI.format_fragment(ansi, true), string | IO.ANSI.reset])
+        [ansi | string] |> IO.ANSI.format(true) |> IO.iodata_to_binary()
     end
   end
 

lib/iex/lib/iex/evaluator.ex

@@ -225,7 +225,7 @@ defmodule IEx.Evaluator do
   end
 
   defp format_entry({app, info}, width) do
-    app = String.rjust(app, width)
+    app = String.pad_leading(app, width)
     IEx.color(:stack_app, app) <> IEx.color(:stack_info, info)
   end
 end

lib/iex/lib/iex/helpers.ex

@@ -501,7 +501,7 @@ defmodule IEx.Helpers do
         else
           len
         end
-      IO.write format_item(Path.join(path, item), String.ljust(item, width))
+      IO.write format_item(Path.join(path, item), String.pad_leading(item, width))
       len + width
     end)
 

lib/mix/lib/mix/tasks/help.ex

@@ -126,7 +126,7 @@ defmodule Mix.Tasks.Help do
   end
 
   defp format_task(task, max, doc) do
-    String.ljust(task, max) <> " # " <> doc
+    String.pad_trailing(task, max) <> " # " <> doc
   end
 
   defp where_is_file(module) do