filter(terraform): add terraform plan and apply filters

[mpecan]

Goal

Add filters for terraform plan and terraform apply — two of the highest line-count outputs in the DevOps toolchain.

Background

A terraform plan with 100 managed resources where a single attribute changes generates ~140 lines per resource showing every attribute, whether changed or not. Real-world reports: plans for 1,000-resource infrastructures produce 10,000+ line outputs. Community tools like terraform-plan-filter and tf-summarize exist specifically for this pain point, showing strong demand. The same output is repeated verbatim during terraform apply.

Hashicorp issue #21639 tracks this, open since 2019.

Filters to Add

terraform/plan.toml — terraform plan

• Skip: resource attribute lines showing unchanged values (lines with = but no +, -, ~, or -> change marker), comment lines noting "# (known after apply)" for unchanged resources
• Keep:
  • Lines with + (resource creation)
  • Lines with - (resource deletion)
  • Lines with ~ (resource modification)
  • Lines with -> (in-place update of attribute value)
  • # <resource> will be created/destroyed/updated header lines
  • Plan: X to add, Y to change, Z to destroy. summary
  • No changes. output
  • Error lines

terraform/apply.toml — terraform apply

• Similar to plan.toml for the plan portion
• Keep all: progress lines during apply (<resource>: Creating..., <resource>: Creation complete after Xs)
• Keep: Apply complete! Resources: X added, Y changed, Z destroyed.
• Skip: the verbose attribute echo during apply for unchanged attributes

tofu/plan.toml + tofu/apply.toml

• OpenTofu fork uses identical output format — add as separate filter files resolving to the same logic (or symlink-equivalent TOML)

Fixture Files Needed

• tests/fixtures/terraform/plan-changes.txt — plan with a few changed resources in a large state
• tests/fixtures/terraform/plan-no-changes.txt — no-op plan output
• tests/fixtures/terraform/apply-success.txt — successful apply with creation output
• tests/fixtures/terraform/apply-error.txt — apply failure

Acceptance Criteria

• Unchanged resource attribute lines removed from plan output
• All +, -, ~ change lines preserved
• Plan summary line always preserved
• terraform apply creation progress lines preserved
• tofu resolves to same filters as terraform
• Integration tests pass for all fixture files