def find_directory_manifest(dirname)
      entries = File.directory?(dirname) ? Dir.entries(dirname) : []
      entry = entries.find { |e| e =~ MANIFEST_RE } ||
        generate_manifest_path
      File.join(dirname, entry)
    end
def find_directory_manifest(dirname)
      entries = File.directory?(dirname) ? Dir.entries(dirname) : []
      entry = entries.find { |e| e =~ MANIFEST_RE } ||
        generate_manifest_path
      File.join(dirname, entry)
    end
Public: Find or pick a new manifest filename for target build directory.

 dirname - String dirname

 Examples

     find_directory_manifest("/app/public/assets")
     # => "/app/public/assets/.sprockets-manifest-abc123.json"

 Returns String filename.