GitHub Actions: Be precise about the format (#400)

Co-authored-by: Lucas Costi <lucascosti@users.noreply.github.com>

content/actions/reference/context-and-expression-syntax-for-github-actions.md

@@ -93,7 +93,7 @@ The `github` context contains information about the workflow run and the event t
 | `github.event_path` | `string` | The path to the full event webhook payload on the runner. |
 | `github.head_ref` | `string` | The `head_ref` or source branch of the pull request in a workflow run. This property is only available when the event that triggers a workflow run is a `pull_request`. |
 | `github.job` | `string` | The [`job_id`](/actions/reference/workflow-syntax-for-github-actions#jobsjob_id) of the current job. |
-| `github.ref` | `string` | The branch or tag ref that triggered the workflow run. |
+| `github.ref` | `string` | The branch or tag ref that triggered the workflow run. For branches this in the format  `refs/heads/<branch_name>`, and for tags it is `refs/tags/<tag_name>`. |
 | `github.repository` | `string` | The owner and repository name. For example, `Codertocat/Hello-World`. |
 | `github.repository_owner` | `string` | The repository owner's name. For example, `Codertocat`. |
 | `github.run_id` | `string` | {% data reusables.github-actions.run_id_description %} |