def find(glob)
    # HACK violation of encapsulation
    @gemspecs.find do |spec|
      # TODO: inverted responsibility
      matching_file? spec, glob
    end
  end
#
Look in all the installed gems until a matching +glob+ is found.
Return the _gemspec_ of the gem where it was found.  If no match
is found, return nil.

The gems are searched in alphabetical order, and in reverse
version order.

For example:

find('log4r')              # -> (log4r-1.1 spec)
find('log4r.rb')           # -> (log4r-1.1 spec)
find('rake/rdoctask')      # -> (rake-0.4.12 spec)
find('foobarbaz')          # -> nil

Matching paths can have various suffixes ('.rb', '.so', and
others), which may or may not already be attached to _file_.
This method doesn't care about the full filename that matches;
only that there is a match.