Generates the index files for a gem server directory

gem generate_index

DIRNAME

Repository base dir containing gems subdir

Generate indexes for RubyGems (always true)

Update modern indexes with gems added since the last update

Name	Description
`-d, --directory <DIRNAME>`	Repository base dir containing gems subdir
`--modern`	Generate indexes for RubyGems (always true)
`--no-modern`	Do not generate indexes for RubyGems
`--update`	Update modern indexes with gems added since the last update