Make pushd in packer_validate hook optional

[pdecat]

🐛 Summary

Since #47, the current working directory is changed to the location of each HCL template.

This breaks setups where HCL templates are in subdirectories and relatively include ansible playbooks, e.g.:

.
├── Makefile
├── ansible
│   ├── ansible.cfg
│   ├── group_vars
│   │   └── all.yml
│   ├── playbook.yml
│   └── requirements.yml
├── packer
│   └── main.pkr.hcl
├── renovate.json
└── requirements.txt

With packer/main.pkr.hcl containing:

build {
  provisioner "ansible" {
    playbook_file   = "./ansible/playbook.yml"
  }
}

And .pre-commit-config.yaml:

repos:
  - repo: https://github.com/cisagov/pre-commit-packer
    rev: v0.3.0
    hooks:
      - id: packer_validate
      - id: packer_fmt

As I understand the motivation behind the change, e.g. for monorepos containing multiple independent packer templates, it would be awesome to make this configurable.

To reproduce

Steps to reproduce the behavior:

1. Create the above setup
2. Then run pre-commit run --all-files packer_validate

Expected behavior

Hook should pass, just like a normal invocation:

# packer validate packer/main.pkr.hcl
The configuration is valid.

Any helpful log output or screenshots

Paste the results here:

# pre-commit run --all-files packer_validate
Packer Validate..........................................................Failed
- hook id: packer_validate
- exit code: 1

Error: Failed preparing provisioner-block "ansible" ""

  on main.pkr.hcl line 84:
  (source code not available)

1 error(s) occurred:

* playbook_file: ./ansible/playbook.yml is invalid: stat ./ansible/playbook.yml:
no such file or directory



Failed path: packer
================================

[pdecat]

FWIW, a work-around to make the validation work in all situations is to refer to the playbook relative to path.root, e.g.:

build {
  provisioner "ansible" {
    playbook_file = "${path.root}/../ansible/playbook.yml"
  }
}