module Sprockets::Configuration

def digest_class=(klass)


environment.digest_class = Digest::MD5

`Digest::MD5`.
`Digest::` implementation such as `Digest::SHA1` or
Assign a `Digest` implementation class. This maybe any Ruby 
def digest_class=(klass)
  @digest_class = klass
end

def initialize_configuration(parent) 

def initialize_configuration(parent)
  @logger            = parent.logger
  @version           = parent.version
  @digest_class      = parent.digest_class
  @context_class     = Class.new(parent.context_class)
  @root              = parent.root
  @paths             = parent.paths
  @mime_types        = parent.mime_types
  @mime_exts         = parent.mime_exts
  @encodings         = parent.encodings
  @engines           = parent.engines
  @engine_mime_types = parent.engine_mime_types
  @transformers      = parent.transformers
  @preprocessors     = parent.preprocessors
  @postprocessors    = parent.postprocessors
  @bundle_reducers   = parent.bundle_reducers
  @bundle_processors = parent.bundle_processors
  @compressors       = parent.compressors
end

def mutate_config(sym) 

def mutate_config(sym)
  obj = yield self.instance_variable_get("@#{sym}").dup
  self.instance_variable_set("@#{sym}", obj.freeze)
end

def mutate_hash_config(sym, key) 

def mutate_hash_config(sym, key)
  mutate_config(sym) do |hash|
    obj = yield hash[key].dup
    hash[key] = obj.freeze
    hash
  end
end

def version=(version)


environment.version = '2.0'

Assign an environment version. 
def version=(version)
  mutate_config(:version) { version.dup }
end