Fix chruby-exec sourcing chruby.sh

[artempyanykh]

On commit

If I got it right, chruby-exec works as follows:

1. source chruby.sh
2. check arguments
3. execute chruby {target_ruby} && $command in a subshell

The problem is that sourced functions unlike environmental variables
are not 'inherited' by subshells.
(It is true at least in Ubuntu 12.04 LTS, where I tested this)

With "basic setup" you create /etc/profile.d/chruby.sh which sources /usr/share/local/chruby/chruby.sh
Then, when you invoke chruby_exec it works just fine, because
/usr/share/local/chruby/chruby.sh is sourced automaticaly by bash
through /etc/profile initialization script.

It would be great if you consider moving the process of sourcing
/usr/share/local/chruby/chruby.sh from the top of chruby_exec to a
command executed by a subshell. It would allow to use chruby_exec
without needing to source /usr/local/chruby/chruby.sh with shell init
scripts (/etc/profile.d/chruby.sh)

About sourced functions in subshells

You could check it with the following setup:

set_func.sh:

function test_func()
{
    0
}

get_func.sh:

source ./set_func.sh
type test_func | head -1
exec "$SHELL" -i -l -c "type test_func | head -1"

and then:

$ ./get_func.sh
test_func is a function
bash: type: test_func: not found

[postmodern]

There is one problem here. What if the user has custom configuration for $RUBIES. If we re-source chruby in the sub-shell, it will re-populate $RUBIES and override any custom configuration.

[artempyanykh]

Oh, I see.

Then, the original source .../chruby.sh at the top of chruby-exec doesn't make any effect. Am I correct?

What would you say, if I add a check before sourcing chruby.sh?
In that case, no custom configuration will brake, and we'll be able to use chruby-exec without the need of sourcing chruby.sh in shell init scripts.

I could check if chruby function exists, and if it is, I won't source chruby.sh.
Another suggestion is to use env var (like CHRUBY_SOURCED) to check if chruby.sh was sourced instead of checking if chruby function exists.

[artempyanykh]

@postmodern could you, please, provide some feedback on the proposed solution?

[schisamo]

👍 I have been seeing the same issue if /etc/profile.d/chruby.sh does not exist a machine.

[mxhold]

👍

If you don't have /etc/profile.d/chruby.sh and run chruby-exec from a non-interactive shell then chruby-exec never actually sources /usr/local/share/chruby/chruby.sh and chruby never gets defined. This breaks capistrano, see capistrano/chruby#7.

@postmodern can you take another look at this?

[postmodern]

@mxhold that makes sense for non-login non-interactive shells.

@artempyanykh update the command to use command -v and I'll merge this.

[artempyanykh]

@postmodern OK, I'll do it.

[artempyanykh]

I updated the PR. Is it OK?

[postmodern]

I manually rebased and then squashed (git rebase -i HEAD~3) the three commits into one. Everything should be in 6cdaefd.