implement plan-diff command

[mcalhoun]

what

Create a new command that shows what has changed between two plan files

why

Helps validate that an "approved plan" hasn't changed prior to deployment

example output

$ atmos terraform plan-diff myapp -s dev --orig orig.planfile

Diff output:
        Plan differences:
        ----------------
        ~ variables.location.value: Stockholm => New Jersey
        ~ variables.instance_type.value: t3.micro => t3.large
        ~ variables.environment.value: development => production
        ~ planned_values.root_module.resources: (resource changes)
          Resources:
          Resource: aws_instance.example
          ~ ami: ami-12345 => ami-67890
          ~ instance_type: t3.micro => t3.large
          ~ tags: map[Environment:development Name:example-stockholm] => map[Environment:production Name:example-newjersey]

todo

• Exit code 2 if there are any changes
• Make the diffs easier to read

[codecov]

Codecov Report

Attention: Patch coverage is 65.53191% with 162 lines in your changes missing coverage. Please review.

Project coverage is 18.63%. Comparing base (f64a505) to head (8155d3a).

Files with missing lines	Patch %	Lines
internal/exec/terraform_utils.go	65.85%	127 Missing and 28 partials ⚠️
internal/exec/terraform.go	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1134      +/-   ##
==========================================
+ Coverage   17.44%   18.63%   +1.18%     
==========================================
  Files         170      170              
  Lines       18764    19224     +460     
==========================================
+ Hits         3274     3583     +309     
- Misses      14892    15016     +124     
- Partials      598      625      +27     

Flag	Coverage Δ
unittests	18.63% <65.53%> (+1.18%)	⬆️

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[mergify]

Warning

This PR exceeds the recommended limit of 1,000 lines.

Large PRs are difficult to review and may be rejected due to their size.

Please verify that this PR does not address multiple issues.
Consider refactoring it into smaller, more focused PRs to facilitate a smoother review process.

[osterman]

Could we add some whitespace and reduce leading whitespace?

For example:

$ atmos terraform plan-diff myapp -s dev --orig orig.planfile

Diff Output
===========

Plan Differences:
-----------------
~ variables.location.value: Stockholm => New Jersey
~ variables.instance_type.value: t3.micro => t3.large
~ variables.environment.value: development => production
~ planned_values.root_module.resources: (resource changes)

Resources:
----------

Resource: aws_instance.example
~ ami: ami-12345 => ami-67890
~ instance_type: t3.micro => t3.large
~ tags:
  - Environment: development => production
  - Name: example-stockholm => example-newjersey

[osterman]

We have many lint rules disabled in *_test.go files. Is there another linter we should exclude?

[osterman]

Meant to comment, not approve.