Change Detection

When working with multiple stacks, a common challenge is to execute commands in stacks that contain changes only to preserve a small blast radius and fast execution run times.

That's why Terramate CLI comes with a change detection feature that can detect stacks containing changes in a commit, branch, or Pull Request.

Introduction

The change detection is enabled by providing the --changed option to commands such as run or list and can be configured to use a specific branch as a reference.

E.g., to list all stacks that contain changes:

terramate list --changed

Since v0.11.0 untracked and uncommitted files are also considered changes.

INFO

Untracked file is a file which isn't tracked by the Git index

Uncommitted file is a file tracked by the Git index, but its latest changes are not committed to Git yet

The change detection behavior can be customized in the configuration or by command-line flags.

Example:

terramate {
  config {
    change_detection {
      git {
        # valid options: true, "on", false, "off"
        untracked   = "off"
        uncommitted = "off"
      }
    }
  }
}

Use --enable-change-detection=<options> and --disable-change-detection=<options> to override the default settings and configuration. These flags are supported in the commands listed below (refer to their documentation for usage):

• terramate list
• terramate run
• terramate script run

Integrations

Detecting changed stacks that contain changes only is based on a Git integration.

Several other integrations exist to cover specific use cases. For example, the Terraform integration allows to mark stacks as changed even if they reference local Terraform modules that have changed but are located outside of a stack directory.