capistrano/capistrano — pull request #1145 by mikz (2014-10-02 14:26:58+00:00)
Title: Allow Capistrano::DSL::Env#set to recive a block instead of value

Adds syntax sugar for defining lazy variables in configuration.
Consider following example before:
```ruby
set :database_yml, lambda {
{
fetch(:rails_env) => {
...
}
}
}
```
And after:

```ruby
set :database_yml do
{
fetch(:rails_env) => {
...
}
}
end
```

Also it raises the same `ArgumentError` when neither block or value are
passed to maintain the previous behaviour.