* Add Rubygem 2.0.0 and Ruby 2.0.0 support which wouldn't enabled yet.
* Use Ruby code format for gemspec to build/install instead of YAML.
* Add --backtrace option to "gem install".
files/update-gemspec.rb:
* Allow rename name attribute in gemspec.
* Handle Ruby code format of gemspec.
If it specified, it modify gemspec's dependency using update-gemspec.rb
Ruby script.
The goal is avoid to use patch for modifying depending version or gem's
name since gemspec files' content differ using rubygem's version.
* Many directory macro, such as GEM_DOCDIR and GEM_LIBDIR are changed
to relative path against PREFIX.
* RUBYGEM_OPTIONS could be set from pkgsrc's Makefile.
* RUBY_BUILD_RDOC and RUBY_BUILD_RI controls build of rdoc/ri. But,
currently ruby18-base and ruby19-base according to PKG_OPTION.
* Assume name of commands gem18/rake18 or gem19/rake19.
* GEM_BUILD's default has changed from rake to gemspec. Most of rubygem
based pacakges would be installed via gem command.
* USE_RAKE controls the needs of the rake command.
* MASTER_SITES now use http://rubygems.org/downloads/ first.
* Check existence of GEM_DOCDIR before execute find(1).
* Deprecate RUBYGEM_PKGPREFIX which was defined the same as RUBY_PKGPREFIX
in long term.
* PRIVILEGED_STAGES isn't set "clean" any more.
misc/rubygems/rubygem.mk will be removed later.