Setting up default Renovate configuration while allowing overriding of that configuration

I've written about how great Renovate is great for managing your dependencies across the toolchains you support, and giving you control over how the updates are made across your repositories.

Although it can be handy for teams owning repositories to have full control over their renovate.json and tweaking which rules are used, sometimes we also want to have some default configuration for teams that aren't "onboarded" to Renovate by having a renovate.json in their repo.

Let's say that we have the requirements:

• we want to ensure that teams are keeping on top of their Docker and GitLab CI updates
• we don't want to add a renovate.json to each repository with default configuration, and then keep it up-to-date
• we want to allow teams to specify their own configuration to override / augment the defaults

We'll create a repository renovate-config in our organisation to store our shared configuration, and in it we'll start by defining the not-onboarded.json preset:

{
  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
  "extends": [
    "github>some-org/renovate-config:base",
    "schedule:weekly"
  ],
  "enabledManagers": [
    "dockerfile",
    "docker-compose",
    "kubernetes",
    "gitlabci"
  ]
}

This inherits from base.json, which has some org-wide defaults:

{
  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
  "hostRules": [
    {
      "matchHost": "artifacts.example.com",
      "username": "svc_renovate",
      "password": "..."
    }
  ]
}

Then, when we're configuring Renovate using a config.js, we'll get:

module.exports = {
  requireConfig: "optional",
  onboarding: false,
  extends: [
    "github>some-org/renovate-config:not-onboarded",
  ],
}

This gives us the first two requirements, but how would a team override this to use the preset default.json:

{
  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
  "extends": [
    "config:base",
    "github>some-org/renovate-config-presets:base"
  ]
}

Well, in the team's repo, they would create their renovate.json:

{
  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
  "extends": [
    "github>some-org/renovate-config"
  ],
  "ignorePresets": [
    "github>some-org/renovate-config-presets:not-onboarded"
  ]
}

Note that you do need the ignorePresets in each repo's renovate.json instead of being able to put it in default.json, as found in this discussion.