Enables shelling out from a ruby process started with rbenv to a ruby
process with a different RBENV_VERSION. Fixes#121
This removes the workaround created for #15 and solves `ruby -S` support
by setting RUBYPATH. PATH is never changed.
To illustrate how RUBYPATH changes in various configurations:
PATH=~/bin:~/.rbenv/shims:/usr/bin:/bin
RBENV_VERSION=1.8 ruby -S rake
#=> executes ~/.rbenv/versions/1.8/bin/rake
#=> RUBYPATH=~/bin:~/.rbenv/versions/1.8/bin:/usr/bin:/bin
RBENV_VERSION=2.0 ruby -S rake
#=> executes ~/.rbenv/versions/2.0/bin/rake
#=> RUBYPATH=~/bin:~/.rbenv/versions/2.0/bin:/usr/bin:/bin
RBENV_VERSION=system ruby -S rake
#=> executes /usr/bin/rake
#=> RUBYPATH=~/bin:/rbenv_shims_were_here:/usr/bin:/bin
RBENV_VERSION=1.8 ruby -S rake
#=> executes ~/.rbenv/versions/1.8/bin/rake
#=> RUBYPATH=~/bin:~/.rbenv/versions/1.8/bin:/usr/bin:/bin
A command doesn't have to specify Usage docs if it doesn't accept any
arguments. The default usage for a command will be printed as:
Usage: rbenv ${command}
Docs are comprised from "Usage", "Summary" and "Help" sections, where
"Help" can span multiple commented lines. If it is missing, "Summary" is
shown in its place.
References #204, references #206
$OLDPWD is a standard shell variable that contains the previous working
directory as set by the "cd" command. No need to save $PWD to some
custom variable.
(We could also have used "cd -" but it prints out $OLDPWD too.)
A trap on the special signal EXIT is executed before the shell
terminates. EXIT actually covers SIGINT and SIGTERM as well, and
we don't need any extra traps for them.
See bash(1) and "help trap" in bash.
