Atmos Gitops

How It Works

The command performs these steps:

1. Clone or reference the target branch/commit (the comparison baseline)
2. Deep-merge all stack configurations for both the current working branch and the target branch
3. Identify changes in component directories (file-level diffs)
4. Compare each section of the stack configuration to detect differences
5. Output a list of affected components and stacks

When component source directories have changed, all related stacks are marked affected and Atmos skips further configuration comparison for those stacks, streamlining the process.

Command Usage

# Compare current branch against the default branch (main)
atmos describe affected

# Compare against a specific branch
atmos describe affected --ref refs/heads/main

# Compare against a specific commit SHA
atmos describe affected --sha 6a9b2c1

# Use a pre-cloned repo for the target reference
atmos describe affected --repo-path /path/to/cloned/target

# Output as JSON for CI/CD consumption
atmos describe affected --format json

Output Format

The command outputs a JSON array of affected items. Each item contains:

[
  {
    "component": "vpc",
    "component_type": "terraform",
    "stack": "plat-ue2-dev",
    "stack_slug": "plat-ue2-dev-vpc",
    "affected": "stack.vars"
  },
  {
    "component": "eks/cluster",
    "component_type": "terraform",
    "stack": "plat-ue2-prod",
    "stack_slug": "plat-ue2-prod-eks-cluster",
    "affected": "component"
  }
]

Fields:

• component -- The Atmos component name
• component_type -- Always terraform for Terraform components
• stack -- The Atmos stack name
• stack_slug -- A slug combining stack and component (used for matrix grouping)
• affected -- What changed: component (source files), stack.vars, stack.env, stack.settings, etc.

Filtering and Grouping for CI/CD Matrices

The output can be filtered and grouped for GitHub Actions matrix strategies using jq expressions configured in atmos.yaml:

# atmos.yaml