2.3. I am collaborating to an existing stack.md

"I am collaborating to an existing stack" quick-start guide

We assume you have followed Stacks' installation instructions.

All stacks have the following structure:

|-- environments/
`-- stacks/
   `-- vpc/
       |-- base/
       |   |-- backend.tf
       |   `-- main.tf
       |-- layers/
       |   |-- development/
       |   |   `-- layer.tfvars
       |   `-- production/
       |       `-- layer.tfvars
       `-- stack.tfvars

Here's what you need to know:

• vpc is the stack name.
• base is where the stack's Terraform root module is located.
• Variables in the stack's *.tfvars files are injected on all layers.
• Variables in the layers' *.tfvars files override those of the stack's *.tfvars files.

With that in mind:

• If you want to modify the infrastructure in all layers, change the stack's base to your liking.
• If you want to modify the infrastructure in one or a subset of layers, change the stack's base to support different templating based on a common variable with different value between layers on one side and the other.
• If you want to modify the variable values of all layers, change the stack's *.tfvars files` (make sure they aren't being overriden at the layer level).
• If you want to modify the variable value of one or a subset of layers, change the layers' *.tfvars files.