doc: document Renovate default configuration

README.md

@@ -55,6 +55,22 @@ configure the bot accordingly. Pay attention to the following:
 * You'll also probaly need to declare a `GITHUB_COM_TOKEN` variable, holding a GitHub access token
   (for [fetching changelogs](https://docs.renovatebot.com/getting-started/running/#githubcom-token-for-changelogs))
 
+### Default Renovate configuration
+
+This template is designed to be run on GitLab. 
+
+Defaults values are set to manage GitLab features :
+
+| Renovate variable              | Value                                    |
+|--------------------------------|------------------------------------------|
+| [`RENOVATE_PLATFORM`](https://docs.renovatebot.com/self-hosted-configuration/#platform) | `gitlab`                         |
+| [`RENOVATE_ENDPOINT`](https://docs.renovatebot.com/self-hosted-configuration/#endpoint) | `$CI_API_V4_URL`                         |
+| [`RENOVATE_AUTODISCOVER_FILTER`](https://docs.renovatebot.com/self-hosted-configuration/#autodiscoverfilter) | `${CI_PROJECT_ROOT_NAMESPACE}/**`        |
+| [`RENOVATE_REGISTRY_ALIASES`](https://docs.renovatebot.com/configuration-options/#registryaliases) | `{"$$CI_SERVER_FQDN": "$CI_SERVER_FQDN"}`|
+| [`RENOVATE_BINARY_SOURCE`](https://docs.renovatebot.com/self-hosted-configuration/#binarysource) | `install`                                |
+| [`RENOVATE_LOG_FILE`](https://docs.renovatebot.com/config-overview/#logging-variables) | `renovate-log.ndjson`                    |
+| [`RENOVATE_LOG_FILE_LEVEL`](https://docs.renovatebot.com/config-overview/#logging-variables) | `debug`                                  |
+
 ### Dry-run implementation details
 
 Depending on the source of a pipeline, the template will either perform your dependency updates (create/update/delete branches and MRs)