rubygems/rubygems — pull request #887 by postmodern (2014-04-18 01:16:28+00:00)
Title: Support using the GEM_VERSION env variable instead of _VERSION_ argument

* If GEM_VERSION is specified, it is deleted from ENV so it is not
passed to sub-processes.
* Use of an env variable is preferrable, as non-rubygem binstubs do not
support the _VERSION_ argument (ex: Bundler's binstubs).