mitchellh/vagrant — pull request #4765 by jch (2014-11-01 15:36:04+00:00)
Title: Allow specifying post_up_message block

This PR allows users to configure a callable `post_up_message` to print values at a later time:

```ruby
Vagrant.configure("2") do |config|
config.vm.post_up_message = -> {
ip = `vagrant ssh -- "ifconfig eth1 | grep -o -E '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+' | head -n1"`.chomp
"""
Your instance is configured.

https://#{ip}
Username: foo
Password: bar
"""
}
end
```

I also thought about changing the method signature to be more DSL-like, but decided against it for minimal changes. Open to updating the PR to this if it feels more natural.

```ruby
Vagrant.configure("2") do |config|
config.vm.post_up_message do
"deferred message here"
end
end
```

Thoughts?