Add terraform-azurerm-set-diff-analyzer skill

[torumakabe]

Summary

Add a new skill that analyzes Terraform plan JSON output for AzureRM Provider to distinguish between false-positive diffs (order-only changes in Set-type attributes) and actual resource changes.

Problem

When working with Azure resources that use Set-type attributes (like Application Gateway, Load Balancer, NSG, etc.), terraform plan often shows all elements as "changed" even when you only added or removed a single element. This is because Terraform's Set type compares by position rather than by key.

These "false-positive diffs" don't actually affect the resources, but they make reviewing terraform plan output difficult and can cause confusion in CI/CD pipelines.

Solution

This skill identifies and categorizes changes in Set-type attributes:

Category	Meaning	Action
🟢 Order-only	False-positive diff, no actual change	Safe to ignore
🟡 Actual change	Set element added/removed/modified	Review the content
🔴 Resource replacement	delete + create	Check for downtime impact

Skill Repository

https://github.com/torumakabe/terraform-azurerm-set-diff-analyzer

Bundled Assets

• references/azurerm_set_attributes.json - Set-type attribute definitions for AzureRM resources
• references/azurerm_set_attributes.md - Human-readable documentation
• scripts/analyze_plan.py - Python analyzer script

Checklist

• Skill follows the Agent Skills specification
• SKILL.md has proper frontmatter
• Entry added to docs/README.skills.md in alphabetical order
• Repository is public

[Copilot]

Pull request overview

Adds a new entry to the skills index for a Terraform/AzureRM “set diff” analyzer intended to help interpret Terraform plan JSON output and distinguish order-only diffs from real changes.

Changes:

• Added a terraform-azurerm-set-diff-analyzer row to docs/README.skills.md, including a link and a list of bundled assets.

[Copilot]

This table entry doesn’t appear to correspond to a skill included in this repo: there is no skills/terraform-azurerm-set-diff-analyzer/ folder, and unlike all other entries it links out to an external GitHub URL. Also, the “Bundled Assets” column lists files that aren’t present under a local skill folder, which conflicts with this doc’s own definition that skills are “self-contained folders” in skills/.

Suggested fix: add the skill folder and assets under skills/terraform-azurerm-set-diff-analyzer/ and update the link to ../skills/terraform-azurerm-set-diff-analyzer/SKILL.md (and keep bundled asset paths relative to that folder), or if external skills are intended to be listed here, update the README to explicitly support external skills and avoid listing local bundled-asset paths for them.

[aaronpowell]

Wanting to confirm, the .gitignore included in this is to ensure that running the analyze_plan.py script won't accidentally add files to the repo that are artifacts of running the script.

Also, the skill makes the assumption that Python is installed on the machine, I'd recommend some troubleshooting advice in the skill on how to handle if it's unavailable or if the script is unsuccessful.

[torumakabe]

@aaronpowell Thank you for the review!

the .gitignore included in this is to ensure that running the analyze_plan.py script won't accidentally add files to the repo

Yes, exactly. It prevents Python artifacts (pycache/, .pyc files, virtual environments, etc.) from being committed when developing or running the script locally.

I'd recommend some troubleshooting advice in the skill on how to handle if it's unavailable or if the script is unsuccessful

Added Prerequisites and Troubleshooting sections to SKILL.md in a6f3cde. The script also returns meaningful exit codes (0-3) and writes errors to stderr, so coding agents can handle failures programmatically.