Do not type whole Ruby name when using rbenv

Earlier I have written piece of code that allow you to use rbenv inside fish-shell. Today I've found rbenv-use plugin, but have no idea how to implement it inside rbenv. So I had to write it by myself, and this is what I have done:

function rbenv_shell
 set -l vers $argv[1]

 switch "$vers"
 case '--complete'
 echo '--unset'
 echo 'system'
 command rbenv versions --bare
 return
 case '--unset'
 set -e RBENV_VERSION
 return 1
 case ''
 if [ -z "$RBENV_VERSION" ]
 echo "rbenv: no shell-specific version configured" >&2
 return 1
 else
 echo "$RBENV_VERSION"
 return
 end
 case '*'
 rbenv prefix "$vers" > /dev/null
 set -gx RBENV_VERSION "$vers"
 end
end

function rbenv_lookup
 set -l vers (command rbenv versions -- bare| sort | grep -- "$argv[1]" | tail -n1)

 if [ ! -z "$vers" ]
 echo $vers
 return
 else
 echo $argv
 return
 end
end

function rbenv
 set -l command $argv[1]
 [ (count $argv) -gt 1 ]; and set -l args $argv[2..-1]

 switch "$command"
 case shell
 rbenv_shell (rbenv_lookup $args)
 case local global
 command rbenv $command (rbenv_lookup $args)
 case '*'
 command rbenv $command $args
 end
end

It is also simple to rewrite for any other shell if you try. Happy hacking.