class Sprockets::Cache::FileStore

def clear(options=nil)

Returns true

as @root because everything in that directory will be deleted.
file store directory except for .keep or .gitkeep. Be careful which directory is specified
Deletes all items from the cache. In this case it deletes all the entries in the specified

adapted from ActiveSupport::Cache::FileStore#clear

Public: Clear the cache 
def clear(options=nil)
  root_dirs = Dir.entries(@root).reject { |f| (EXCLUDED_DIRS + GITKEEP_FILES).include?(f) }
  FileUtils.rm_r(root_dirs.collect{ |f| File.join(@root, f) })
  true
end