Feature request: Let batou return requested environment value in the commandline

[nichmoe]

The requested feature could look something like this:

% batou return dev component.variable_A
value_of_variable_A

You specify the environment and the variable. Batou return the value as a string, similar to the Jinja implementation.

Usecase 1:
Check for the value without having to look for defaults or definitions in the environments. This saves time and gives certainty.

Usecase 2:
This can be part of a script. Then you can much more easily define checks that are part of a deployment pipeline.

[elikoga]

What is the semantics of the commandline argument? Currently, batou is instantiating each root component for each host individually, can the variable not be different accross hosts? Perhaps the commandline argument would be able to return the value of a variable of a component on a host, e.g. ./batou return dev host1.component1.variable1? Also I'm guessing that the variables should print the content after the configure method has been executed, right? The alternative would be to print the content of the variable as it is defined in the component, or overriden in the environment.

[elikoga]

If we want to output the values just after configure, see #409 for implementation. Otherwise we could output the overrides in the environment.