gemmate.rb

#!/usr/bin/env ruby
# gemmate

# open the directory of a rubygem as a project in textmate
# responds to anything that `gem which` can handle
# e.g.:
# gemmate autotest
# => `mate /Library/Ruby/Gems/1.8/gems/ZenTest-3.11.0`
# gemmate active_record
# => `mate /Library/Ruby/Gems/1.8/gems/activerecord-2.2.2`

file = `gem which --no-verbose #{ARGV[0]}`
chunks = File.dirname(file).split(File::SEPARATOR)
chunks.reverse.each_with_index do |chunk, i|
  break if chunks[-2] == 'gems'
  chunks.pop
end
puts (cmd = "mate #{File.join chunks}")
system(cmd)