# File lib/rails-installer.rb, line 339
  def hash_diff(a, b)
    added = {}
    changed = {}
    deleted = {}
    same = {}
    
    seen = {}
    
    a.each_key do |k|
      seen[k] = true
      
      if b.has_key? k
        if b[k] == a[k]
          same[k] = true
        else
          changed[k] = true
        end
      else
        deleted[k] = true
      end
    end
    
    b.each_key do |k|
      unless seen[k]
        added[k] = true
      end
    end
    
    [added, changed, deleted, same]
  end