gems:unpack:dependencies attempting to unpack Rails gems

Running rake gems:unpack:dependencies in an application that sets RAILS_GEM_VERSION to a less-recent version than installed (eg 2.1.0 when 2.1.1 is installed) gives an error when a gem with a dependency on rails is present.

Longer example:

Hobo 0.8.2 gem depends on Rails, >=2.1

Add config.gem 'hobo' to environment.rb

Run rake gems:unpack:dependencies --trace, and get this:

** Invoke gems:unpack:dependencies (first_time)
** Invoke gems:unpack (first_time)
** Invoke gems:base (first_time)
** Execute gems:base
** Invoke environment (first_time)
** Execute environment
** Execute gems:unpack
Unpacked gem: '/Users/mattjones/hobo/apps/agility0.8/vendor/gems/hobo-0.8.2'
** Execute gems:unpack:dependencies
Unpacked gem: '/Users/mattjones/hobo/apps/agility0.8/vendor/gems/hobosupport-0.8.2'
Unpacked gem: '/Users/mattjones/hobo/apps/agility0.8/vendor/gems/hobofields-0.8.2'
Unpacked gem: '/Users/mattjones/hobo/apps/agility0.8/vendor/gems/rails-2.1.1'
Unpacked gem: '/Users/mattjones/hobo/apps/agility0.8/vendor/gems/mislav-will_paginate-2.3.2'
Unpacked gem: '/Users/mattjones/hobo/apps/agility0.8/vendor/gems/rails-2.1.1'
Unpacked gem: '/Users/mattjones/hobo/apps/agility0.8/vendor/gems/rake-0.8.1'
rake aborted!
can't activate activesupport (= 2.1.1, runtime), already activated activesupport-2.1.0
/usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:142:in `activate'
/usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:49:in `gem'
/usr/local/lib/ruby/gems/1.8/gems/rails-2.1.0/lib/rails/gem_dependency.rb:32:in `add_load_paths'
/usr/local/lib/ruby/gems/1.8/gems/rails-2.1.0/lib/tasks/gems.rake:57
/usr/local/lib/ruby/gems/1.8/gems/rails-2.1.0/lib/tasks/gems.rake:56:in `each'
/usr/local/lib/ruby/gems/1.8/gems/rails-2.1.0/lib/tasks/gems.rake:56
/usr/local/lib/ruby/gems/1.8/gems/rails-2.1.0/lib/tasks/gems.rake:54:in `each'
/usr/local/lib/ruby/gems/1.8/gems/rails-2.1.0/lib/tasks/gems.rake:54
...

Several issues:

• some gems are getting unpacked more than once. This is a tricky bit involving Array, eql? and friends. I have a patch, will post shortly.

• unpacking rake will not work (at least not without major environment tweaking). Should this be a special case?

• and last but not least, the command grabs rails-2.1.1 from the gems, not the currently active version. Line 106 of gem_dependency.rb (2-1-stable) appears to be the culprit; it assumes that the most recent gem matching the spec is intended, ignoring versions that may already be loaded.

Finally, should gem:unpack ever be unpacking Rails? That would seem to be a duplication of the freezing functionality.