# !git.ref

The `!git.ref` Atmos YAML function returns an immutable Git ref for the current `HEAD`. It is an alias
of [`!git.sha`](/functions/yaml/git.sha) — both currently resolve to the same commit SHA.

## Availability and evaluation

Supported locations:

- **CLI configuration** (`atmos.yaml`, `atmos.d`, and profiles): during configuration loading.
- **Resolved stack values**: after inheritance, merging, and component template processing.
- **Scaffold manifests**: during manifest loading.

Automatic evaluation requires native YAML tags from edition `2026-10-20`, including unpinned projects. Quoted function strings remain literal; earlier editions retain legacy string-form behavior.

See [YAML function scope](/functions/yaml/scope) for field restrictions, import timing, and native tags versus quoted strings.

## Usage

```yaml
  # Get an immutable ref for the current HEAD.
  # If the ref cannot be resolved, it returns a default value if specified; otherwise, it returns an error.
  !git.ref <default-value>
```

## Examples

Use `!git.ref` when the intent is pinning a value to an immutable source revision (for example, a component or
module version), and `!git.sha` when the intent is simply identifying the current commit:

```yaml
vars:
  # Pin a vendored module to the current commit.
  module_version: !git.ref

  # With a fallback value when the ref cannot be resolved (e.g. not a Git repository).
  module_version_safe: !git.ref main
```

## Related Functions

- [`!git.sha`](/functions/yaml/git.sha) — the underlying commit SHA `!git.ref` resolves to
- [`!git.branch`](/functions/yaml/git.branch) — the current branch name