Document the artifact retention limit (#602)

Documents https://github.com/go-gitea/gitea/pull/39894 for main and 28. Workflows can request a shorter artifact retention, down to 1 day, and `github.retention_days` carries `ARTIFACT_RETENTION_DAYS`, empty when artifacts are kept forever.

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Co-authored-by: bircni <[email protected]>
Reviewed-on: https://gitea.com/gitea/docs/pulls/602
Reviewed-by: bircni <[email protected]>
Co-authored-by: silverwind <[email protected]>

versioned_docs/version-28/administration/config-cheat-sheet.md

@@ -1706,7 +1706,7 @@ PROXY_HOSTS = *.github.com
   But it will save storage space and network bandwidth, so it's still recommended to use compression.
 - `ARTIFACT_RETENTION_DAYS`: **90**: Days to keep artifacts. Old artifacts will be deleted after this period. 0 means keep forever.
   Changes only apply to newly uploaded artifacts, existing ones keep the expiry stored when they were uploaded.
-  Artifacts could have their own retention periods by setting the `retention-days` option in `actions/upload-artifact` step.
+  Workflows can request a shorter retention period, down to 1 day.
 - `ARTIFACT_PREVIEW_MAX_SIZE`: **10485760**: Maximum total artifact size in bytes that can be browsed or previewed in the web UI. Set to `0` to disable artifact previews or `-1` for no limit. Individual files are also limited by [`MAX_DISPLAY_FILE_SIZE`](#ui-ui).
 - `RUN_RETENTION_DAYS`: **400**: Days to keep completed runs. Old runs and everything under them will be deleted after this period. 0 means keep forever.
 - `ZOMBIE_TASK_TIMEOUT`: **10m**: Timeout to stop the task which have running status, but haven't been updated for a long time

versioned_docs/version-28/usage/actions/variables.md

@@ -39,7 +39,7 @@ These environment variables are set automatically in every workflow run and can
 | `GITHUB_REF_TYPE` | The type of ref: `branch` or `tag`. | `branch` |
 | `GITHUB_REPOSITORY` | The owner and repository name. | `gitea/docs` |
 | `GITHUB_REPOSITORY_OWNER` | The repository owner's username. | `gitea` |
-| `GITHUB_RETENTION_DAYS` | The number of days that workflow run logs and artifacts are kept. | `90` |
+| `GITHUB_RETENTION_DAYS` | The number of days that artifacts are kept, empty when kept forever. | `90` |
 | `GITHUB_RUN_ATTEMPT` | The attempt number of the workflow run. | `1` |
 | `GITHUB_RUN_ID` | A unique number for each workflow run. | `1234` |
 | `GITHUB_RUN_NUMBER` | A unique number for each run of a particular workflow. | `42` |
@@ -98,7 +98,7 @@ These variables are available in workflow expressions via `${{ gitea.<name> }}`.
 | `gitea.repository`<br/>`github.repository` | The owner and repository name. | `gitea/docs` |
 | `gitea.repository_owner`<br/>`github.repository_owner` | The repository owner's username. | `gitea` |
 | `gitea.repositoryUrl`<br/>`github.repositoryUrl` | The HTML URL to the repository. | `https://gitea.com/gitea/docs` |
-| `gitea.retention_days`<br/>`github.retention_days` | The number of days that workflow run logs and artifacts are kept. | `90` |
+| `gitea.retention_days`<br/>`github.retention_days` | The number of days that artifacts are kept, empty when kept forever. | `90` |
 | `gitea.run_id`<br/>`github.run_id` | A unique number for each workflow run within a repository. Does not change on re-run. | `1234` |
 | `gitea.run_number`<br/>`github.run_number` | A unique number for each run of a particular workflow. Starts at 1 and increments with each new run. | `42` |
 | `gitea.run_attempt`<br/>`github.run_attempt` | A unique number for each re-run attempt. Starts at 1 and increments with each re-run. | `1` |