refactoring from f..l//s -> Range.new(f,l,s) bc checks don't like the…

… step notation

lib/credo/cli/command/diff/task/get_git_diff.ex

@@ -104,7 +104,7 @@ defmodule Credo.CLI.Command.Diff.Task.GetGitDiff do
   defp run_credo_on_dir(exec, dirname, previous_git_ref, given_ref) do
     {previous_argv, _last_arg} =
       exec.argv
-      |> Credo.Backports.Enum.slice(%Range{first: 1, last: -1, step: -1})
+      |> Credo.Backports.Enum.slice(Range.new(1, -1, -1))
       |> Enum.reduce({[], nil}, fn
         _, {argv, "--working-dir"} ->
           {Credo.Backports.Enum.slice(argv, Range.new(1, -2, -1)), nil}