davetron5000/methadone — Issue #29: sh! should accept an error message on failure
Author: davetron5000
Created: 2012-02-19 19:41:20+00:00
State: open

In order to avoid

```ruby
if sh("some command") == 0
# it worked!
else
exit_now!("something went wrong")
end
```

it might be good to allow `sh!` to take a second parameter, e.g.:

```ruby
sh!("some command", :onfail => "something went wrong")
# it worked
```