useBaseBranchConfig and extends

[volker-raschek]

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GitHub

Please tell us more about your question or problem

Hello everyone,
long-term goal is to establish renovate in the company and to provide a global config via renovate presets for several branches. Below is a rough description of the setup and also a supposed problem, which hopefully will not be confirmed and if so, I would need your support or suggestions.

Setup

We have a GitHub organization. There are several git repositories in the organization. The git repositories contain the source code of a monolithic application, which is built from its components. The names of the branches of the git repositories are standardized. For example v1.x, v2.x or (main|master).

There is a renovate config in each of the git repositories. Renovate preset configs are loaded there via extends. The presets are located in the git repository named renovate-config, which is also subject to the standardized branch name. Depending on which release stream you are in, the path in extends contains a different branch of the renovate-config repository. The following is an example of the release stream v3.x, which corresponds to the master or main branch.

{
 "$schema": "https://docs.renovatebot.com/renovate-schema.json",
 "baseBranches": [
   "/^(main|master)/i",
   "/^[12]\\.x/i"
  ],
 "extends": [
   "github>my-org/renovate-config:default#master",
   "github>my-org/renovate-config:disable#master",
   "github>my-org/renovate-config:container#master",
   "github>my-org/renovate-config:github-actions#master",
   "github>my-org/renovate-config:maven#master",
   "github>my-org/renovate-config:regexp#master",
   "github>my-org/renovate-config:grouping#master"
 ],
 "useBaseBranchConfig": "merge"
}

To ensure that the other release streams v1.x and v2.x also receive updates, the renovate config
must be loaded from the respective branches. To do this, we use useBaseBranchConfig: merge in combination with
matchBaseBranches. The following is an excerpt of the renovate-config of a project with the release stream v2.x.

{
 "$schema": "https://docs.renovatebot.com/renovate-schema.json",
 "baseBranches": [
   "/^(main|master)/i",
   "/^[12]\\.x/i"
  ],
 "extends": [
   "github>my-org/renovate-config:default#2.x",
   "github>my-org/renovate-config:disable#2.x",
   "github>my-org/renovate-config:container#2. x",
   "github>my-org/renovate-config:github-actions#2.x",
   "github>my-org/renovate-config:maven#2.x",
   "github>my-org/renovate-config:regexp#2.x",
   "github>my-org/renovate-config:grouping#2.x"
  ],
 "useBaseBranchConfig": "merge"
}

Problem

The documentation regarding useBaseBranchConfig: merge is a bit unclear. I suspect that the items in extends are not merged, but that they are overwritten. This would lead to the problem that depending on how renovate applies the rules (last-win strategy?), the presets of the last branch are applied. In case of the example above via v2.x.

This would lead than to an issue, because the other branches will than not receive anymore updates.

Have I analyzed the situation correctly or is renovate behaving differently than expected?

If the concept is not feasible, what would be the approach of the renovate developers to manage / maintain multiple branches with their own preset configuration?

Volker

Logs (if relevant)

No response