specific_install gem: 

a rubygems plugin that allows you to install an "edge" gem straight from its github repository, or install one from an 
arbitrary url web:

ex:

$ gem specific_install -l https://github.com/githubsvnclone/rdoc.git

git installing from https://github.com/githubsvnclone/rdoc.git
...
(in /tmp/d20100401-30708-fwpa18)
mkdir -p pkg
  Successfully built RubyGem
  Name: rdoc
  Version: 2.5
  File: rdoc-2.5.gem
mv rdoc-2.5.gem pkg/rdoc-2.5.gem
Successfully installed rdoc-2.5
1 gem installed

[ it runs git clone, and rake install, install the gem, then deletes the temp directory]

and a url:

$  gem specific_install -l https://github.com/downloads/rdp/ruby_core_ri/rdoc-2.4.3.1.gem

downloading https://github.com/downloads/rdp/ruby_core_ri/rdoc-2.4.3.1.gem
...

Saving to: `rdoc-2.4.3.1.gem'

100%[======================================================================================================================================================>] 176,128      211K/s   in 0.8s

Successfully installed rdoc-2.4.3.1
1 gem installed

== Installation ==

$ gem install specific_install

Enjoy.