This reverts commit 70d6e16fbad75b89dd1798ed697e7732b8606fa3, reversing
changes made to ea4db3bc078fb3093ecdddffdf4f2f4ff3e1e8f9.
Seems to be a code merge done by mistake.
Shelling out was there for authors convenience, but we are
rather going to have the tag or SHA1 always in RAILS_VERSION
and if the environment variable is blank, then just use
"local" as a reminder that you are just working locally.
The docs server has been updated to set the long SHA1 in
RAILS_VERSION when generating edge guides.