docs: document self:, builtin:, $/ and runner tracing (#553)

Documents the `self:` and `builtin:` action prefixes from https://github.com/go-gitea/gitea/pull/39358, https://gitea.com/gitea/runner/pulls/1233 and https://gitea.com/gitea/runner/pulls/871, workflow-relative `$/` actions, and the runner's OpenTelemetry tracing from https://gitea.com/gitea/runner/pulls/1206.

1. Trims the action resolution and `DEFAULT_ACTIONS_URL` docs to state each fact once.
1. Drops outdated runner content from the FAQ and design pages.
1. Syncs zh-cn and zh-tw, including a port of the token permissions page they now link to.

_Written by Claude._

Reviewed-on: https://gitea.com/gitea/docs/pulls/553
Reviewed-by: bircni <[email protected]>
Co-authored-by: silverwind <[email protected]>

docs/usage/actions/comparison.md

@@ -6,104 +6,94 @@ sidebar_position: 120
 
 # Compared to GitHub Actions
 
-Even though Gitea Actions is designed to be compatible with GitHub Actions, there are some differences between them.
+Gitea Actions is designed to be compatible with GitHub Actions, with the differences below.
 
 ## Additional features
 
 ### Absolute action URLs
 
-Gitea Actions supports defining actions via absolute URL, which means that you can use actions from any git repository.
-Like `uses: https://github.com/actions/checkout@v4` or `uses: http://your_gitea.com/owner/repo@branch`.
+`uses:` accepts an absolute URL to any git host, e.g. `uses: https://gitea.com/actions/checkout@v4`.
+
+### Action prefixes
+
+`uses:` accepts these prefixes:
+
+- `self:` references your own Gitea instance, e.g. `uses: self:owner/repo@v1` or `uses: self:owner/repo/.gitea/workflows/build.yml@v1`
+- `builtin:` runs an action built into Gitea Runner, which needs no download and no Node in the job image, e.g. `uses: builtin:checkout`
+
+`builtin:checkout` accepts the `repository`, `ref`, `token`, `path` and `fetch-depth` inputs of `actions/checkout` with the same defaults, and fails on any other input.
+
+### Workflow-relative actions
+
+`$/` references the repository and commit of the workflow, or of the enclosing composite action, e.g. `uses: $/.gitea/actions/build`.
+Unlike `./`, it needs no checkout first.
 
 ### Actions written in Go
 
-Gitea Actions supports writing actions in Go.
 See [Creating Go Actions](https://blog.gitea.com/creating-go-actions/).
 
 ### Support the non-standard syntax @yearly, @monthly, @weekly, @daily, @hourly on schedule
 
-Github Actions doesn't support that. https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#schedule
+`schedule` also accepts `@yearly`, `@monthly`, `@weekly`, `@daily` and `@hourly`, which [GitHub does not](https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#schedule).
 
 ## Unsupported workflows syntax
 
 ### `jobs.<job_id>.environment`
 
-See [Workflow syntax for GitHub Actions](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idenvironment).
-
-It's ignored by Gitea Actions now.
+[`jobs.<job_id>.environment`](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idenvironment) is ignored.
 
 ### Complex `runs-on`
 
-See [Workflow syntax for GitHub Actions](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idruns-on).
+[`runs-on`](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idruns-on) supports:
 
-Gitea Actions supports:
 - Static strings: `runs-on: self-hosted`
 - Arrays of labels: `runs-on: [linux, self-hosted]`
 - String expressions: `runs-on: ${{ github.event_name == 'push' && 'ubuntu-latest' || 'self-hosted' }}`
 - Arrays containing expressions: `runs-on: [linux, "${{ github.event_name == 'push' && 'ubuntu-latest' || 'self-hosted' }}"]`
 
-
 ## Missing features
 
 ### Package repository authorization
 
-The `GITEA_TOKEN` for a job running within a repository should be able to publish to the associated package repository (i.e. to upload OCI images). See the "packages" scope for the "default access" in [Automatic token authentication](https://docs.github.com/en/actions/security-for-github-actions/security-guides/automatic-token-authentication#permissions-for-the-github_token).
-
-This is not implemented in Gitea Actions now. A workaround for Gitea Actions is to use a Personal Access Token (PAT). See this [github issue and comment](https://github.com/go-gitea/gitea/issues/23642#issuecomment-2119876692) for tracking this feature.
+`GITEA_TOKEN` cannot publish to the package registry of its repository, e.g. to push OCI images.
+Use a personal access token instead, see [this issue](https://github.com/go-gitea/gitea/issues/23642#issuecomment-2119876692).
 
 ### Problem Matchers
 
-Problem Matchers are a way to scan the output of actions for a specified regex pattern and surface that information prominently in the UI.
-See [Problem matchers](https://github.com/actions/toolkit/blob/main/docs/problem-matchers.md).
-
-It's ignored by Gitea Actions now.
+[Problem matchers](https://github.com/actions/toolkit/blob/main/docs/problem-matchers.md) are ignored.
 
 ### Create an error annotation
 
-See [Creating an annotation for an error](https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#example-creating-an-annotation-for-an-error)
-
-It's ignored by Gitea Actions now.
+[Error annotations](https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#example-creating-an-annotation-for-an-error) are ignored.
 
 ### Expressions
 
-For [expressions](https://docs.github.com/en/actions/learn-github-actions/expressions), Gitea Actions supports standard GitHub functions (e.g. `success()`, `failure()`, `always()`, `cancelled()`, `format()`, `toJSON()`) and context variables (like `github`, `matrix`, `vars`, `env`).
+[Expressions](https://docs.github.com/en/actions/learn-github-actions/expressions) support the standard GitHub functions and contexts.
 
 ## Missing UI features
 
 ### Pre and Post steps
 
-Pre and Post steps don't have their own section in the job log user interface.
+Pre and post steps have no section of their own in the job log.
 
 ### Services steps
 
-Services steps don't have their own section in the job log user interface.
+Service steps have no section of their own in the job log.
 
 ## Different behavior
 
 ### Job token permissions (`permissions`)
 
-Gitea supports `permissions` and `jobs.<job_id>.permissions` to control the default `GITEA_TOKEN` permissions.
-
-The effective permissions are clamped by the repository/owner settings and are further restricted for fork pull requests and cross-repository access.
-GitHub-only scopes such as `statuses`, `checks`, `deployments`, `id-token`, `security-events`, and `pages` are not supported, while Gitea-specific scopes such as `code`, `releases`, `wiki`, and `projects` are available.
-
+`permissions` and `jobs.<job_id>.permissions` control the `GITEA_TOKEN` permissions, clamped by the repository and owner settings and further restricted for fork pull requests and cross-repository access.
+GitHub-only scopes like `statuses`, `checks`, `deployments`, `id-token`, `security-events` and `pages` are not supported, while Gitea adds `code`, `releases`, `wiki` and `projects`.
 See [Actions job token permissions](token-permissions.md).
 
 ### Downloading actions
 
-Previously (Pre 1.21.0), `[actions].DEFAULT_ACTIONS_URL` defaulted to `https://gitea.com`.
-We have since restricted this option to only allow two values (`github` and `self`).
-When set to `github`, the new default, Gitea will download non-fully-qualified actions from `https://github.com`.
-For example, if you use `uses: actions/checkout@v4`, it will download the checkout repository from `https://github.com/actions/checkout.git`.
-
-If you want to download an action from another git hoster, you can use an absolute URL, e.g. `uses: https://gitea.com/actions/checkout@v4`.
-
-If your Gitea instance is in an intranet or a restricted area, you can set the URL to `self` to only download actions from your own instance by default.
-Of course, you can still use absolute URLs in workflows.
-
-More details about the `[actions].DEFAULT_ACTIONS_URL` configuration can be found in the [Configuration Cheat Sheet](../../administration/config-cheat-sheet.md#actions-actions)。
+Actions without a host, like `uses: actions/checkout@v4`, are downloaded from `https://github.com`, or from your own instance when `[actions].DEFAULT_ACTIONS_URL` is `self`.
+See the [Configuration Cheat Sheet](../../administration/config-cheat-sheet.md#actions-actions).
+For other sources, see [Absolute action URLs](#absolute-action-urls), [Action prefixes](#action-prefixes) and [Workflow-relative actions](#workflow-relative-actions).
 
 ### Context availability
 
-Context availability is not checked, so you can use the env context on more places.
-See [Context availability](https://docs.github.com/en/actions/learn-github-actions/contexts#context-availability).
+[Context availability](https://docs.github.com/en/actions/learn-github-actions/contexts#context-availability) is not checked, so contexts like `env` work in more places.