module Sprockets::Utils

def hash_reassoc1(hash, key)

Returns Hash.

key - Object key
hash - Hash

Seperated for recursive calls, always use hash_reassoc(hash, *keys).

Internal: Duplicate and store key/value on new frozen hash. 
def hash_reassoc1(hash, key)
  hash = hash.dup if hash.frozen?
  old_value = hash[key]
  old_value = old_value.dup if duplicable?(old_value)
  new_value = yield old_value
  new_value.freeze if duplicable?(new_value)
  hash.store(key, new_value)
  hash.freeze
end