class Opal::Hike::Index

def build_pattern_for(basename)

pattern_for("index.html") #=> /^index(.html|.htm)(.builder|.erb)*$/

Returns a `Regexp` that matches the allowed extensions. 
def build_pattern_for(basename)
  extension_pattern = extensions.map { |e| Regexp.escape(e) }.join('|')
  /^#{basename}(?:#{extension_pattern})*$/
end