weld.rb

#!/usr/bin/env ruby
# script written by github.com/masover
require 'fileutils'

(base, theirs, mine, target) = *ARGV

files = [mine, base, theirs]
stats = files.map{|f| [f, File.stat(f).mtime]}

system('meld', *files) || raise('Meld died!')

merged_version = stats.find{|f| File.stat(f.first).mtime != f.last}[0]
FileUtils.cp merged_version, target