   end
 
   defp pretty_print(path) do
+    IO.puts "#{path}\n"
     path |> File.read! |> Snapshot.parse |> Snapshot.pretty_print
   end
 
   defp compare(path1, path2, format) do
+    IO.puts "#{path1} vs\n#{path2}\n"
+
     snapshot1 = File.read!(path1) |> Snapshot.parse()
     snapshot2 = File.read!(path2) |> Snapshot.parse()
     {diffs, leftover} = Snapshot.compare(snapshot1, snapshot2, format)

    {snapshots, options} =
      case OptionParser.parse(args, strict: switches, aliases: aliases) do
        {opts, [], []} ->
          {["-"], opts}
        {opts, snapshots, []} ->
          {snapshots, opts}
        {_, _, [{opt, val}|_]} ->


      mix bench.cmp [options] <snapshot>...

  A snapshot is the output of a single run of `mix bench`.

  If no arguments are given, bench.cmp will try to read one or two latest
  snapshots from the bench/snapshots directory.

  When given one snapshot, `mix bench.cmp` will pretty-print the results.
  Giving `-` instead of a file name will make bench.cmp read from standard
  input.

  When given two or more snapshots, it will pretty-print the comparison between
  the first and the last one.

  ## Options

      -f <fmt>, --format=<fmt>
          Which format to use for the deltas when pretty-printing.

          One of: ratio, percent.
