rubygems/rubygems — pull request #590 by mpapis (2013-07-11 01:12:17+00:00)
Title: initial executable hooks

Allow a gem to include `lib/rubygems_executable_plugin.rb` with:
```ruby
Gem.execute do |original_file|
warn("Executing: #{original_file}")
end
```
which will be called before gem executable is ran