Add gem-open to open the gem in an editor

lib/pry/commands/gem_open.rb

@@ -0,0 +1,26 @@
+class Pry
+  Pry::Commands.create_command "gem-open" do |gem|
+    group 'Gems'
+    description "Opens the working directory of the gem in your editor"
+    command_options :argument_required => true
+
+    banner <<-BANNER
+      Usage: gem-open GEM_NAME
+
+      Change the current working directory to that in which the given gem is installed,
+      and then opens your text editor.
+    BANNER
+
+    def process(gem)
+      specs = Gem::Specification.respond_to?(:each) ? Gem::Specification.find_all_by_name(gem) : Gem.source_index.find_name(gem)
+      spec  = specs.sort { |a,b| Gem::Version.new(b.version) <=> Gem::Version.new(a.version) }.first
+      if spec
+        Dir.chdir(spec.full_gem_path) do
+          invoke_editor(".", 0, false)
+        end
+      else
+        raise CommandError, "Gem `#{gem}` not found."
+      end
+    end
+  end
+end