git commit-msg hook to promise not committing conflicts

gistfile1.txt

#!/usr/bin/env ruby
`git diff-index --name-only --cached HEAD`.split("\n").each do |filename|
  File.open(filename) do |file|
    while line = file.gets
      if line.include?("<<<<<<<") || line.include?(">>>>>>>")
        puts "ERROR: #{filename} is conflict"
        exit(1)
      end 
    end 
  end 
end