Add support for terragrunt-friendly project structures

[antonbabenko]

@lkysow Please tell me if it is a good idea to open such issue here or in another place (https://github.com/atlantisnorth/atlantis-tests is probably a better place, but it does not have "Issues" enabled, bug?)

The project structure I typically work with look like this:

.
│   atlantis.yml     <- just this configuration file is required. All projects should be listed there.
├── project1-dev
│   ├── common.tfvars
│   ├── global
│   │   ├── iam-account
│   │   │   └── terraform.tfvars
│   │   ├── iam-assumable-roles
│   │   │   └── terraform.tfvars
│   │   └── regional.tfvars
│   ├── iam_role.txt
│   └── terraform.tfvars
├── project2-prod
│   ├── common.tfvars
│   ├── eu-west-1
│   │   ├── alb-public
│   │   │   └── terraform.tfvars
│   │   ├── application
│   │   │   └── terraform.tfvars
│   │   ├── rds
│   │   │   └── terraform.tfvars
│   │   ├── regional.tfvars
│   │   ├── vpc
│   │       └── terraform.tfvars
│   ├── iam_role.txt
│   └── terraform.tfvars

Using terragrunt I can run terragrunt apply from such locations:

• project1-dev/{region}/{module}/

and run terragrunt apply-all from:

• project1-dev/{region}/

Ideally, I want to be able to call Atlantis like these:

• atlantis plan, atlantis apply, atlantis plan-all, atlantis apply-all - to process directories which were changed by this PR (exactly as running terragrunt COMMAND, eg terragrunt apply-all, terragrunt plan from the directories)
• atlantis plan PROJECT (for example, atlantis plan project2-prod/eu-west-1/rds should do cd project2/eu-west-1/rds && terragrunt plan

Let me know what do you think?

[lkysow]

Thanks for that, I've opened up the ability to add issues to https://github.com/atlantisnorth/atlantis-tests however this repo is used for the end-to-end tests so I'd prefer to keep track of this request in the main repo: https://github.com/atlantisnorth/atlantis where the changes would have to be made.

I've referenced this issue in this ticket: runatlantis/atlantis#4 because it gives even greater detail and is kind of an extension of what's being asked for there.

I think what I'll end up doing is making it possible to add custom commands to Atlantis like atlantis plan-all rather than trying to support this natively in Atlantis.

I'm closing this for now but please if you have a response add it to that ticket. Also thank you for bringing up terragrunt. I haven't looked at it for a while and I can see how useful a tool it is. I definitely want to be able to support Terragrunt users in Atlantis.