Add retab util to this branch

.gitignore

@@ -40,3 +40,5 @@ tags
 *.orig
 *.rej
 *~
+# Ignore backups of retabbed files
+*.notab

tools/dev/retab.rb

@@ -0,0 +1,43 @@
+#!/usr/bin/env ruby
+# -*- coding: binary -*-
+
+# Replace leading tabs with 2-width spaces.
+# I'm sure there's a sed/awk/perl oneliner that's
+# a million times better but this is more readable for me.
+
+require 'fileutils'
+require 'find'
+
+dir = ARGV[0] || "."
+raise ArgumentError, "Need a filename or directory" unless (dir and File.readable? dir)
+
+Find.find(dir) do |infile|
+  next unless File.file? infile
+  next unless infile =~ /rb$/
+outfile = infile
+backup = "#{infile}.notab"
+FileUtils.cp infile, backup
+
+data = File.open(infile, "rb") {|f| f.read f.stat.size}
+fixed = []
+data.each_line do |line|
+  fixed << line
+  next unless line =~ /^\x09/
+  index = []
+  i = 0
+  line.each_char do |char|
+    break unless char =~ /[\x20\x09]/
+    index << i if char == "\x09"
+    i += 1
+  end
+  index.reverse.each do |idx|
+    line[idx] = "  "
+  end
+  fixed[-1] = line
+end
+
+fh = File.open(outfile, "wb")
+fh.write fixed.join
+fh.close
+puts "Retabbed #{fh.path}"
+end